Pre-U
Pre-U 9795
Specimen
Q7
8 marks
Challenging +1.2
The equation
$$8x^3 + 12x^2 + 4x - 1 = 0$$
has roots \(\alpha, \beta, \gamma\). Show that the equation with roots \(2\alpha + 1, 2\beta + 1, 2\gamma + 1\) is
$$y^3 - y - 1 = 0.$$ [3]
The sum \((2\alpha + 1)^n + (2\beta + 1)^n + (2\gamma + 1)^n\) is denoted by \(S_n\). Find the values of \(S_3\) and \(S_{-2}\). [5]