The Quadratic Function

34 questions

1.26: Past-paper question 5

4PM1/1/June/2025 — Question 5 · 8 marks

(a) Show that (α+β)33αβ(α+β)=α3+β3\displaystyle (\alpha + \beta)^3 - 3\alpha\beta(\alpha + \beta) = \alpha^3 + \beta^3
(2)
The quadratic equation 2x26x7=0\displaystyle 2x^2 - 6x - 7 = 0 has roots α\displaystyle \alpha and β\displaystyle \beta
Without solving the equation
(b) form a quadratic equation, with integer coefficients, which has roots α2β\displaystyle \frac{\alpha^2}{\beta} and β2α\displaystyle \frac{\beta^2}{\alpha}
(6)

1.28: Past-paper question 2

4PM1/1/November/2025 — Question 2 · 5 marks

f(x)=2x210x+7f(x) = 2x^2 - 10x + 7
Given that f(x)\displaystyle f(x) can be written in the form f(x)=a(x+b)2+c\displaystyle f(x) = a(x+b)^2 + c where a\displaystyle a, b\displaystyle b and c\displaystyle c are rational numbers,
(a) find the value of a\displaystyle a, the value of b\displaystyle b and the value of c\displaystyle c
(3)
(b) Hence, or otherwise, write down
(i) the minimum value of f(x)\displaystyle f(x)
(ii) the value of x\displaystyle x at which this minimum value occurs.
(2)

1.29: Past-paper question 7

4PM1/1/November/2025 — Question 7 · 10 marks

(a) Show that (α+β)(α2αβ+β2)=α3+β3\displaystyle (\alpha + \beta)(\alpha^2 - \alpha\beta + \beta^2) = \alpha^3 + \beta^3
(1)
The equation 2x2+8xk=0\displaystyle 2x^2 + 8x - k = 0 has roots α\displaystyle \alpha and β\displaystyle \beta and where k\displaystyle k is a constant
Given that α3+β3=94\displaystyle \alpha^3 + \beta^3 = -94
(b) show that k=5\displaystyle k = 5
(4)
Given that α>β\displaystyle \alpha > \beta and without solving the equation 2x2+8xk=0\displaystyle 2x^2 + 8x - k = 0
(c) (i) show that αβ=26\displaystyle \alpha - \beta = \sqrt{26}
(3)
(ii) hence find the exact value of α3β3\displaystyle \alpha^3 - \beta^3
(2)

1.27: Past-paper question 8

4PM1/1R/June/2025 — Question 8 · 15 marks

f(x)=2x24x+9f(x) = 2x^2 - 4x + 9
The curve C\displaystyle C has equation y=f(x)\displaystyle y = f(x)
The line l\displaystyle l with equation y8x+9=0\displaystyle y - 8x + 9 = 0 is a tangent to C\displaystyle C
The line k\displaystyle k is perpendicular to l\displaystyle l and is also the tangent to C\displaystyle C at the point where x=p\displaystyle x = p
(a) Find the value of p\displaystyle p
(5)
(b) Show that
(i)(α+β)3=α3+β3+3αβ(α+β)(i) (\alpha + \beta)^3 = \alpha^3 + \beta^3 + 3\alpha\beta(\alpha + \beta)
(ii)α4+β4=((α+β)22αβ)22(αβ)2(ii) \alpha^4 + \beta^4 = \left((\alpha + \beta)^2 - 2\alpha\beta\right)^2 - 2(\alpha\beta)^2
(2)
The quadratic equation f(x)=0\displaystyle f(x) = 0 has roots α\displaystyle \alpha and β\displaystyle \beta
Without solving the equation and using your results from part (b)
(c) form a quadratic equation with integer coefficients, that has roots
α3βandβ3α\alpha^3 - \beta \mathrm{and} \beta^3 - \alpha
(8)

1.21: Past-paper question 2

4PM1/1/June/2024 — Question 2 · 5 marks

f(x)=2x2+4x+9f(x) = 2x^2 + 4x + 9
Given that f(x)\displaystyle f(x) can be written in the form A(x+B)2+C\displaystyle A(x + B)^2 + C, where A\displaystyle A, B\displaystyle B and C\displaystyle C are integers,
(a) find the value of A\displaystyle A, the value of B\displaystyle B and the value of C\displaystyle C
(3)
(b) Hence, or otherwise, find
(i) the value of x\displaystyle x for which 1f(x)\displaystyle \frac{1}{f(x)} is a maximum
(ii) the maximum value of 1f(x)\displaystyle \frac{1}{f(x)}
(2)

1.25: Past-paper question 10

4PM1/1/November/2024 — Question 10 · 18 marks

Given that f(x)\displaystyle f(x) can be expressed in the form AB(x+C)2\displaystyle A - B(x + C)^2 where A\displaystyle A, B\displaystyle B and C\displaystyle C are positive constants
(a) find the value of A\displaystyle A, the value of B\displaystyle B and the value of C\displaystyle C
(4)
(b) Hence write down the maximum value of f(x)\displaystyle f(x)
(1)
The equation f(x)=0\displaystyle f(x) = 0 has roots α\displaystyle \alpha and β\displaystyle \beta
Without solving the equation f(x)=0\displaystyle f(x) = 0
(c) form a quadratic equation, with integer coefficients, that has roots 3αβ\displaystyle \frac{3\alpha}{\beta} and 3βα\displaystyle \frac{3\beta}{\alpha}
(6)
(d) Show that (x+y)3=x3+y3+3xy(x+y)\displaystyle (x + y)^3 = x^3 + y^3 + 3xy(x + y)
(1)
g(x)=3x2+qx+r\displaystyle g(x) = 3x^2 + qx + r where q\displaystyle q and r\displaystyle r are constants
The equation g(x)=0\displaystyle g(x) = 0 has roots α2β\displaystyle \alpha^2 - \beta and β2α\displaystyle \beta^2 - \alpha where α\displaystyle \alpha and β\displaystyle \beta are the roots of the equation f(x)=0\displaystyle f(x) = 0
(e) Using your answer to part (d), find in simplified exact form, the value of q\displaystyle q and the value of r\displaystyle r
(6)

1.22: Past-paper question 10

4PM1/1R/June/2024 — Question 10 · 12 marks

The quadratic equation 2x2+kx+4=0\displaystyle 2x^2 + kx + 4 = 0 has roots α\displaystyle \alpha and β\displaystyle \beta such that
k<0andα>βk < 0 \mathrm{and} \alpha > \beta
Given that α2β2=7174\displaystyle \alpha^2 - \beta^2 = \frac{7\sqrt{17}}{4}
(a) show that k=7\displaystyle k = -7
(8)
(b) Hence form a quadratic equation that has roots
(αβ)and(α+β)(\alpha - \beta) \mathrm{and} (\alpha + \beta)
(4)

1.23: Past-paper question 2

4PM1/2/June/2024 — Question 2 · 8 marks

The quadratic equation 3x25x+1=0\displaystyle 3x^2 - 5x + 1 = 0 has roots α\displaystyle \alpha and β\displaystyle \beta
Without solving the equation,
form a quadratic equation with integer coefficients, that has roots α2β\displaystyle \frac{\alpha}{2\beta} and β2α\displaystyle \frac{\beta}{2\alpha}
(8)

1.18: (a) Express in the form where and are rational numbers to be found.

4PM1/1/November/2023 — Question 2 · 7 marks

g(x)=2x2+12x3g(x) = 2x^2 + \frac{1}{2}x - 3
(a) Express g(x)\displaystyle g(x) in the form p(x+q)2+r\displaystyle p(x+q)^2 + r where p,q\displaystyle p, q and r\displaystyle r are rational numbers to be found.
(3)
(b) Find
(i) the minimum value of g(x)\displaystyle g(x)
(ii) the value of x\displaystyle x at which this minimum occurs.
(2)
h(x)=2x6+12x33h(x) = 2x^6 + \frac{1}{2}x^3 - 3
(c) Hence, or otherwise, write down
(i) the minimum value of h(x)\displaystyle h(x)
(ii) the value of x\displaystyle x at which this minimum occurs.
(2)

1.14: Past-paper question 2

4PM1/1R/June/2023 — Question 2 · 8 marks

One solution to the following simultaneous equations
y=px+96x2xy=5\begin{aligned}y &= px + 9 \\ 6x^2 - xy &= 5\end{aligned}
is (12,q)\displaystyle \left(-\frac{1}{2}, q\right), where p\displaystyle p is an integer and q\displaystyle q is a prime number.
(a) Find the value of p\displaystyle p and the value of q\displaystyle q
(4)
(b) Hence find the other solution to the equations.
(4)

1.15: Past-paper question 11

4PM1/2/June/2023 — Question 11 · 12 marks

The roots of a quadratic equation E\displaystyle E are α\displaystyle \alpha and β\displaystyle \beta where α>β>0\displaystyle \alpha > \beta > 0
Given that αβ=26\displaystyle \alpha - \beta = 2\sqrt{6} and α2+β2=30\displaystyle \alpha^2 + \beta^2 = 30
(a) show that
(i)αβ=3(i) \alpha\beta = 3
(4)
(ii)α+β=6(ii) \alpha + \beta = 6
(2)
(b) Without solving E\displaystyle E
(i) find the value of α4+β4(i) \text{ find the value of } \alpha^4 + \beta^4
(2)
(ii) find the exact value of α4β4(ii) \text{ find the exact value of } \alpha^4 - \beta^4
(2)
Given that α4=P+Q6\displaystyle \alpha^4 = P + Q\sqrt{6} where P\displaystyle P and Q\displaystyle Q are positive integers,
(c) find the value of P\displaystyle P and the value of Q\displaystyle Q
(2)

1.19: The equation where is a constant, has real unequal roots.

4PM1/2/November/2023 — Question 1 · 5 marks

The equation kx2+8x+3k=0\displaystyle kx^2 + 8x + 3k = 0 where k\displaystyle k is a constant, has real unequal roots.
Find the set of values of k\displaystyle k giving your answer in an exact simplified form.
(5)

1.20: Past-paper question 10

4PM1/2/November/2023 — Question 10 · 10 marks

The roots of a quadratic equation are α\displaystyle \alpha and β\displaystyle \beta where
α+β=52andα3+β3=1158\alpha + \beta = -\frac{5}{2} \quad \mathrm{and} \quad \alpha^3 + \beta^3 = \frac{115}{8}
(a) Show that αβ=4\displaystyle \alpha\beta = 4
(3)
(b) Form a quadratic equation with integer coefficients, that has roots
α2+1βandβ2+1α\frac{\alpha^2 + 1}{\beta} \quad \mathrm{and} \quad \frac{\beta^2 + 1}{\alpha}
(7)

1.17: Past-paper question 6

4PM1/2R/June/2023 — Question 6 · 10 marks

f(x)=2x2+5xpf(x) = 2x^2 + 5x - p
The equation f(x)=0\displaystyle f(x) = 0 has roots α\displaystyle \alpha and β\displaystyle \beta
Given that α3+β3=2158\text{Given that } \alpha^3 + \beta^3 = -\frac{215}{8}
(a) find the value of p\displaystyle p
(5)
Without solving the equation f(x)=0\displaystyle f(x) = 0
(b) form a quadratic equation, with integer coefficients, that has roots
α+βα2andα+ββ2\frac{\alpha + \beta}{\alpha^2} \quad \mathrm{and} \quad \frac{\alpha + \beta}{\beta^2}
(5)

1.1: Areas in a flag design

4PM1/1/June/2022 — Question 2 · 9 marks

1.1 diagram 1
Figure 1 shows the design for a flag consisting of a white cross on a grey background. AEFG\displaystyle AEFG and DLMN\displaystyle DLMN are squares with sides of length 3xcm\displaystyle 3x\,\mathrm{cm}. BPQR\displaystyle BPQR and CTUV\displaystyle CTUV are rectangles with sides of length 5xcm\displaystyle 5x\,\mathrm{cm} and 3xcm\displaystyle 3x\,\mathrm{cm}. The width of the cross is ycm\displaystyle y\,\mathrm{cm}.
The total area of the flag is Hcm2\displaystyle H\,\mathrm{cm}^2.
(a) Write down an expression, in terms of x\displaystyle x and y\displaystyle y, for H\displaystyle H.
(1)
Given that the area of the cross is Kcm2\displaystyle K\,\mathrm{cm}^2,
(b) show that
K=14xy+y2.K=14xy+y^2.
(3)
The total area of the flag is to be 3432cm2\displaystyle 3432\,\mathrm{cm}^2 and the area of the cross is to be 1080cm2\displaystyle 1080\,\mathrm{cm}^2.
(c) Find the value of x\displaystyle x and the value of y\displaystyle y.
(5)

1.2: Perimeter and area inequalities for a rectangle

4PM1/1R/June/2022 — Question 4 · 7 marks

1.2 diagram 1
Figure 2 shows a rectangle with width x\displaystyle x metres and length (x+4)\displaystyle (x+4) metres. Its perimeter is P\displaystyle P metres and its area is Am2\displaystyle A\,\mathrm{m}^2.
(a) Find, in terms of x\displaystyle x, an expression for
(i) P\displaystyle P,
(ii) A\displaystyle A.
(2)
The perimeter has to be less than 30\displaystyle 30 metres. The area has to be greater than 12m2\displaystyle 12\,\mathrm{m}^2.
(b) Find the set of possible values for x\displaystyle x. Give your answer in the form
a<x<b.a<x<b.
(5)

1.4: Relations between the roots of a quadratic

4PM1/2/June/2022 — Question 5 · 9 marks

The roots of the quadratic equation
2x2+(6+2p)x+2p=02x^2+(6+2p)x+2p=0
are α\displaystyle \alpha and β\displaystyle \beta.
(a) Write down an expression in terms of p\displaystyle p for
(i) α+β\displaystyle \alpha+\beta,
(ii) αβ\displaystyle \alpha\beta.
(2)
(b) Show that
(αβ)2=9+2p+p2.(\alpha-\beta)^2=9+2p+p^2.
(4)
Given that αβ=3\displaystyle \alpha-\beta=3,
(c) find the possible values of p\displaystyle p.
(3)

1.6: Transform the roots of a quadratic

4PM1/1/June/2021 — Question 6 · 10 marks

(a) Show that
(αβ)2=(α+β)24αβ.(\alpha-\beta)^2=(\alpha+\beta)^2-4\alpha\beta.
(3)
The quadratic equation
x27kx+k2=0,x^2-7kx+k^2=0,
where k\displaystyle k is a positive constant, has roots α\displaystyle \alpha and β\displaystyle \beta, where α>β\displaystyle \alpha>\beta.
(b) Show that
αβ=3k5.\alpha-\beta=3k\sqrt5.
(3)
(c) Hence form a quadratic equation with roots α+1\displaystyle \alpha+1 and β1\displaystyle \beta-1. Give your equation in the form
x2+px+q=0,x^2+px+q=0,
where p\displaystyle p and q\displaystyle q should be given in terms of k\displaystyle k.
(4)

1.7: Complete the square and find a maximum

4PM1/2/June/2021 — Question 2 · 6 marks

f(x)=2+45x125x2.f(x)=2+\frac{4}{5}x-\frac{1}{25}x^2.
Given that f(x)\displaystyle f(x) can be expressed in the form
AB(x+C)2,A-B(x+C)^2,
where A\displaystyle A, B\displaystyle B and C\displaystyle C are constants,
(a) find the value of A\displaystyle A, the value of B\displaystyle B and the value of C\displaystyle C.
(4)
(b) Hence write down
(i) the maximum value of f(x)\displaystyle f(x),
(ii) the value of x\displaystyle x for which this maximum occurs.
(2)

1.8: Complete the square and find an enclosed area

4PM1/1/November/2020 — Question 7 · 13 marks

f(x)=x29x+14.f(x)=x^2-9x+14.
Given that f(x)\displaystyle f(x) can be written in the form (x+a)2+b\displaystyle (x+a)^2+b, where a\displaystyle a and b\displaystyle b are constants,
(a) find the value of a\displaystyle a and the value of b\displaystyle b.
(2)
(b) Hence, or otherwise, find
(i) the minimum value of f(x)\displaystyle f(x),
(ii) the value of x\displaystyle x for which this minimum occurs.
(2)
The curve C\displaystyle C has equation y=f(x)\displaystyle y=f(x). The line l\displaystyle l has equation y=x+5\displaystyle y=x+5.
(c) Use algebra to find the coordinates of the points of intersection of C\displaystyle C and l\displaystyle l.
(4)
(d) Use algebraic integration to find the exact area of the finite region bounded by C\displaystyle C and l\displaystyle l.
(5)

1.9: A quadratic curve and a straight line

4PM1/1R/November/2020 — Question 2 · 11 marks

(a) Express
x2+4x8x^2+4x-8
in the form (x+a)2+b\displaystyle (x+a)^2+b, where a\displaystyle a and b\displaystyle b are constants whose values are to be found.
(2)
(b) Use algebra to solve the simultaneous equations
y=x2+4x8,y=2x+7.y=x^2+4x-8, \qquad y=2x+7.
(5)
Using the same axes and the results of parts (a) and (b),
(c) sketch the curve y=x2+4x8\displaystyle y=x^2+4x-8 and the line y=2x+7\displaystyle y=2x+7, showing clearly the coordinates of the turning point and the points of intersection.
(4)

1.10: Transform the roots of a quadratic

4PM1/1R/November/2020 — Question 8 · 7 marks

f(x)=3x2x+4,g(x)=x2px+q.f(x)=3x^2-x+4, \qquad g(x)=x^2-px+q.
The roots of the quadratic equation f(x)=0\displaystyle f(x)=0 are α\displaystyle \alpha and β\displaystyle \beta.
The roots of the quadratic equation g(x)=0\displaystyle g(x)=0 are
(α+1α)and(β+1β).\left(\alpha+\frac1\alpha\right) \qquad \text{and} \qquad \left(\beta+\frac1\beta\right).
Without solving the equation f(x)=0\displaystyle f(x)=0,
(a) show that
p=712,p=\frac{7}{12},
(3)
(b) find the value of q\displaystyle q.
(4)

1.11: Equations whose roots are transformations of quadratic roots

4PM1/2/November/2020 — Question 6 · 11 marks

f(x)=4x23x5.f(x)=4x^2-3x-5.
The equation f(x)=0\displaystyle f(x)=0 has roots α\displaystyle \alpha and β\displaystyle \beta.
Without solving the equation f(x)=0\displaystyle f(x)=0,
(a) form an equation, with integer coefficients, that has roots
2αβand2βα.\frac{2\alpha}{\beta} \qquad \text{and} \qquad \frac{2\beta}{\alpha}.
(6)
g(x)=4x2+px+q,g(x)=4x^2+px+q,
where p\displaystyle p and q\displaystyle q are constants.
Given that the equation g(x)=0\displaystyle g(x)=0 has roots 3α+β\displaystyle 3\alpha+\beta and α+3β\displaystyle \alpha+3\beta,
(b) find the value of p\displaystyle p and the value of q\displaystyle q.
(5)

1.12: Tangents and normals to a quadratic curve

4PM1/2R/November/2020 — Question 6 · 15 marks

1.12 diagram 1
The curve C\displaystyle C with equation
y=x25x+4y=x^2-5x+4
crosses the x\displaystyle x-axis at the points A\displaystyle A and B\displaystyle B, as shown in Figure 3.
(a) Find the coordinates of A\displaystyle A and B\displaystyle B.
(3)
The tangent to C\displaystyle C at A\displaystyle A meets the tangent to C\displaystyle C at B\displaystyle B at T\displaystyle T.
(b) Find the coordinates of T\displaystyle T.
(6)
The normal to C\displaystyle C at A\displaystyle A meets the normal to C\displaystyle C at B\displaystyle B at N\displaystyle N.
(c) Find the coordinates of N\displaystyle N.
(3)
(d) Find the area of quadrilateral ATBN\displaystyle ATBN.
(3)

1.13: Real roots and transformed roots

4PM1/2R/November/2020 — Question 7 · 12 marks

(a) Find the set of values of k\displaystyle k for which the equation
kx24x+2k=7kx^2-4x+2k=7
has real roots.
(4)
Given that the roots of the equation are α\displaystyle \alpha and β\displaystyle \beta,
(b) form a quadratic equation with roots
α+1αandβ+1β.\frac{\alpha+1}{\alpha} \qquad \text{and} \qquad \frac{\beta+1}{\beta}.
Give each coefficient in terms of k\displaystyle k.
(8)

1.30: Completing the Square and Minimum Value

4PM1/1/June/2019 — Question 5 · 5 marks

The function f\displaystyle f is defined by
f(x)=3x29x+5.f(x)=3x^2-9x+5.
Given that
f(x)=a(xb)2+c,f(x)=a(x-b)^2+c,
where a\displaystyle a, b\displaystyle b and c\displaystyle c are constants,
(a) find the value of a\displaystyle a, the value of b\displaystyle b and the value of c\displaystyle c.
(3)
(b) Hence write down
(i) the minimum value of f(x)\displaystyle f(x),
(ii) the value of x\displaystyle x for which the minimum value occurs.
(2)

1.33: Completing the Square and Unequal Roots

4PM1/1/January/2019 — Question 5 · 10 marks

f(x)=2x2+7x4.f(x)=2x^2+7x-4.
Given that f(x)\displaystyle f(x) can be written in the form
A(x+B)2+C,A(x+B)^2+C,
(a) find the value of A\displaystyle A, the value of B\displaystyle B and the value of C\displaystyle C.
(3)
(b) Write down
(i) the minimum value of f(x)\displaystyle f(x),
(ii) the value of x\displaystyle x at which this minimum occurs.
(2)
The equation
f(x)=px6f(x)=px-6
has unequal real roots.
(c) Find the set of possible values of p\displaystyle p.
(5)

1.31: Algebraic Relations between Quadratic Roots

4PM1/2/June/2019 — Question 10 · 15 marks

The roots of the equation
x2+3x5=0x^2+3x-5=0
are α\displaystyle \alpha and β\displaystyle \beta.
(a) Without solving the equation, find
(i) the value of α2+β2\displaystyle \alpha^2+\beta^2,
(ii) the value of α4+β4\displaystyle \alpha^4+\beta^4.
(5)
Given that α>β\displaystyle \alpha>\beta and without solving the equation,
(b) show that
αβ=29.\alpha-\beta=\sqrt{29}.
(2)
(c) Factorise α4β4\displaystyle \alpha^4-\beta^4 completely.
(3)
(d) Hence find the exact value of α4β4\displaystyle \alpha^4-\beta^4.
(2)
Given that
β4=p+q29,\beta^4=p+q\sqrt{29},
where p\displaystyle p and q\displaystyle q are positive constants,
(e) find the value of p\displaystyle p and the value of q\displaystyle q.
(3)

1.34: Quadratic Roots and a Transformed Equation

4PM1/2/January/2019 — Question 8 · 11 marks

The roots of the equation
3x22x1=03x^2-2x-1=0
are α\displaystyle \alpha and β\displaystyle \beta, where α>β\displaystyle \alpha>\beta.
Without solving the equation,
(a) find the value of α2+β2\displaystyle \alpha^2+\beta^2.
(3)
(b) Show that
αβ=43.\alpha-\beta=\frac43.
(2)
(c) Form a quadratic equation, with integer coefficients, that has roots
α+βαandαββ.\frac{\alpha+\beta}{\alpha} \qquad \text{and} \qquad \frac{\alpha-\beta}{\beta}.
(6)

1.32: Quadratic Roots with Parameters

4PM1/2R/June/2019 — Question 11 · 12 marks

The quadratic equation
x2px+q=0,x^2-px+q=0,
where p>0\displaystyle p>0, has roots α\displaystyle \alpha and β\displaystyle \beta.
Given that
2αβ=32\alpha\beta=3
and that
4(α2+β2)=k26k3,4(\alpha^2+\beta^2)=k^2-6k-3,
where k>3\displaystyle k>3,
(a)
(i) write down the value of q\displaystyle q,
(ii) find an expression, in terms of k\displaystyle k, for p\displaystyle p.
(5)
Given also that
7αβ=3(α+β),7\alpha\beta=3(\alpha+\beta),
(b) find the value of k\displaystyle k.
(2)
(c) Hence form an equation, with integer coefficients, which has roots
αα+βandβα+β.\frac{\alpha}{\alpha+\beta} \qquad \text{and} \qquad \frac{\beta}{\alpha+\beta}.
(5)