# Roots of a cubic equation

• January 3rd 2010, 12:02 PM
Math-DumbassX
Roots of a cubic equation
Right The First Question Is :

1. Given that x=-2 and x=1 are two root of the equation x3+px2-6x+q=0, establish the values of p and q and hence find the third root of the equation

Can Someone Please Show Me How To Do It ... Would Be Much Appreciated :) x
• January 3rd 2010, 12:59 PM
pickslides
expand $(x+2)(x-1)(x+a)$ and equate coefficents to $x^3+px^2-6x+q$