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)