Sketching Polynomials

15 questions

1.10: Past-paper question 5

4PM1/2R/June/2025 — Question 5 · 8 marks

f(x)=x3+x2+x+cwherec is a constantf(x) = x^3 + x^2 + x + c \quad \mathrm{where} c \text{ is a constant}
The remainder when f(x)\displaystyle f(x) is divided by (x2)\displaystyle (x - 2) is 4 times the remainder when
f(x)\displaystyle f(x) is divided by (x+1)\displaystyle (x + 1)
(a) Show that c=6\displaystyle c = 6
(4)
Given that (x+2)\displaystyle (x + 2) is a factor of f(x)\displaystyle f(x)
(b) show that the equation f(x)=0\displaystyle f(x) = 0 has only one real root.
(4)

1.7: Past-paper question 1

4PM1/2/June/2024 — Question 1 · 6 marks

f(x)=6x313x2+ax10wherea is a constantf(x) = 6x^3 - 13x^2 + ax - 10 \quad \mathrm{where} a \text{ is a constant}
Given that (3x2)\displaystyle (3x - 2) is a factor of f(x)\displaystyle f(x)
(a) show that a=21\displaystyle a = 21
(2)
(b) Hence show algebraically that the curve y=f(x)\displaystyle y = f(x) has only one intersection with the x\displaystyle x-axis.
(4)

1.8: Past-paper question 4

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

1.8 diagram 1
Figure 2 shows part of the curve with equation y=x2312x\displaystyle y = \frac{x^2}{3} - \frac{1}{2x} for 4<x<0\displaystyle -4 < x < 0
By drawing a suitable straight line on the grid, obtain estimates, to one decimal place,
of the roots of the equation 4x3+3x236x6=0\displaystyle 4x^3 + 3x^2 - 36x - 6 = 0 in the interval 4<x<0\displaystyle -4 < x < 0
(4)

1.9: where and are constants.

4PM1/2R/June/2024 — Question 4 · 11 marks

f(x)=px3+qx237x12q\displaystyle f(x) = px^3 + qx^2 - 37x - 12q where p\displaystyle p and q\displaystyle q are constants.
When f(x)\displaystyle f'(x) is divided by (x+2)\displaystyle (x + 2) the remainder is 33\displaystyle -33
Given that (x+5)\displaystyle (x + 5) is a factor of f(x)\displaystyle f(x)
(a) (i) show that p=2\displaystyle p = 2
(ii) find the value of q\displaystyle q
(6)
(b) Hence, use algebra to factorise f(x)\displaystyle f(x) completely.
(3)
(c) Hence solve the equation f(x)=0\displaystyle f(x) = 0
(2)

1.4: Past-paper question 3

4PM1/1/June/2023 — Question 3 · 5 marks

1.4 diagram 1
Figure 1 shows part of the curve with equation y=x2+4x2\displaystyle y = \frac{x}{2} + \frac{4}{x^2} in the interval 0.8<x<7\displaystyle 0.8 < x < 7
By drawing a suitable straight line on the grid, obtain an estimate, to one decimal place, of the roots of the equation 3x312x2+8=0\displaystyle 3x^3 - 12x^2 + 8 = 0 in the interval 0.8<x<7\displaystyle 0.8 < x < 7
(5)

1.5: Past-paper question 8

4PM1/1/June/2023 — Question 8 · 9 marks

f(x)=18x22x+13f'(x) = 18x^2 - 2x + 13
Given that (2x1)\displaystyle (2x - 1) is a factor of f(x)\displaystyle f(x)
show that the curve with equation y=f(x)\displaystyle y = f(x) has only one intersection with the x\displaystyle x-axis.
(9)

1.6: Past-paper question 3

4PM1/1/November/2023 — Question 3 · 8 marks

g(x)=mx210x37wherem is an integerg'(x) = mx^2 - 10x - 37 \quad \mathrm{where} m \text{ is an integer}
The curve y=g(x)\displaystyle y = g(x) passes through the point with coordinates (1,20)\displaystyle (1, 20)
Given that (x5)\displaystyle (x-5) is a factor of g(x)\displaystyle g(x)
(a) show that g(x)=2x35x237x+60\displaystyle g(x) = 2x^3 - 5x^2 - 37x + 60
(5)
(b) Hence, or otherwise, use algebra to solve the equation g(x)=0\displaystyle g(x) = 0
(3)

1.1: Determine a polynomial and its real roots

4PM1/2R/June/2022 — Question 4 · 8 marks

f(x)=x3+px2+qx+7,f(x)=x^3+px^2+qx+7,
where p\displaystyle p and q\displaystyle q are integers. (x+1)\displaystyle (x+1) is a factor of f(x)\displaystyle f(x). The remainder when f(x)\displaystyle f(x) is divided by (x+2)\displaystyle (x+2) is 5\displaystyle -5.
(a) Find the value of p\displaystyle p and the value of q\displaystyle q.
(5)
(b) Hence show that f(x)=0\displaystyle f(x)=0 has only one real root.
(3)

1.2: Factors of a polynomial

4PM1/2/June/2021 — Question 6 · 13 marks

f(x)=x3+(p+1)x210x+q,f(x)=x^3+(p+1)x^2-10x+q,
where p\displaystyle p and q\displaystyle q are integers.
Given that (x3)\displaystyle (x-3) is a factor of f(x)\displaystyle f(x),
(a) show that
9p+q+6=0.9p+q+6=0.
(3)
Given that (x+p)\displaystyle (x+p), where p>0\displaystyle p>0, is also a factor of f(x)\displaystyle f(x),
(b) show that
p2+10p+q=0.p^2+10p+q=0.
(3)
(c) Hence find the value of p\displaystyle p and the value of q\displaystyle q.
(5)
(d) Using your values of p\displaystyle p and q\displaystyle q, factorise f(x)\displaystyle f(x) completely.
(2)

1.3: Use remainders to determine and factorise a cubic

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

f(x)=x3+px+q,f(x)=x^3+px+q,
where p\displaystyle p and q\displaystyle q are constants. The remainder when f(x)\displaystyle f(x) is divided by (x1)\displaystyle (x-1) is 12\displaystyle -12. The remainder when f(x)\displaystyle f(x) is divided by (x4)\displaystyle (x-4) is 30\displaystyle 30.
(a) Find the value of p\displaystyle p and the value of q\displaystyle q.
(6)
Using your values of p\displaystyle p and q\displaystyle q,
(b) show that f(3)=0\displaystyle f(3)=0,
(1)
(c) express f(x)\displaystyle f(x) as a product of linear factors,
(3)
(d) hence solve f(x)=0\displaystyle f(x)=0.
(1)

1.11: Factorising a Cubic Polynomial

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

The function f\displaystyle f is defined by
f(x)=x3+2x25x6.f(x)=x^3+2x^2-5x-6.
(a) Factorise
x2x2.x^2-x-2.
(1)
(b) Hence, or otherwise, show that (x2x2)\displaystyle (x^2-x-2) is a factor of f(x)\displaystyle f(x).
(3)

1.14: Expanding and Solving a Cubic Equation

4PM1/1/January/2019 — Question 3 · 5 marks

f(x)=(2x+1)(x2+5x3).f(x)=(2x+1)(x^2+5x-3).
(a) Show that
f(x)=2x3+11x2x3.f(x)=2x^3+11x^2-x-3.
(2)
(b) Hence use algebra to solve the equation
2x3+11x2x3=0.2x^3+11x^2-x-3=0.
Give your roots to 3 decimal places where appropriate.
(3)

1.15: A Rational Curve, Asymptotes and a Tangent

4PM1/1/January/2019 — Question 8 · 15 marks

A curve C\displaystyle C has equation
y=5x32x1,x12.y=\frac{5x-3}{2x-1}, \qquad x\ne\frac12.
(a) Write down an equation of the asymptote to C\displaystyle C that is
(i) parallel to the y\displaystyle y-axis,
(ii) parallel to the x\displaystyle x-axis.
(2)
(b) Find the coordinates of the points of intersection of C\displaystyle C with the coordinate axes.
(2)
(c) Using calculus show that at every point on the curve, the gradient of C\displaystyle C is positive.
(4)
(d) Using the axes provided, sketch C\displaystyle C, showing clearly the asymptotes and the coordinates of the points of intersection of C\displaystyle C with the coordinate axes.
(3)
The line l\displaystyle l is the tangent to C\displaystyle C at the point on the curve where x=1\displaystyle x=1.
(e) Find an equation of l\displaystyle l, giving your answer in the form
y=mx+c.y=mx+c.
(4)

1.12: Cubic Roots and a Parameter

4PM1/2R/June/2019 — Question 1 · 7 marks

f(x)=(x3)[x2+(p2)x+q].f(x)=(x-3)\left[x^2+(p-2)x+q\right].
Given that f(0)=12\displaystyle f(0)=-12,
(a) find the value of q\displaystyle q.
(2)
(b) Find the range of values of p\displaystyle p for which the cubic equation f(x)=0\displaystyle f(x)=0 has only one real root.
(5)

1.13: A Rational Function and Its Asymptotes

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

1.13 diagram 1
Figure 1 shows part of the curve S\displaystyle S with equation
y=ax+bx+c,y=\frac{ax+b}{x+c},
where a\displaystyle a, b\displaystyle b and c\displaystyle c are integers.
The asymptote to S\displaystyle S parallel to the x\displaystyle x-axis is y=2\displaystyle y=-2.
The asymptote to S\displaystyle S parallel to the y\displaystyle y-axis is x=3\displaystyle x=-3.
The curve crosses the x\displaystyle x-axis at (4,0)\displaystyle (4,0).
The curve crosses the y\displaystyle y-axis at (0,p)\displaystyle (0,p), where p\displaystyle p is rational.
Find
(i) a\displaystyle a,
(ii) b\displaystyle b,
(iii) c\displaystyle c,
(iv) p\displaystyle p.
(4)