(a) x = +/- 3 (or 0)
-Because x is being squared, it does not matter if it is positive or negative, as when any number is squared the product is always positive.
3x^2 - 9x = 0
3x(x - 3) = 0
x = 0
x = +/- 3
(b) x = 6, -4
x^2 - 2x - 24 = 0
(x - 6)(x + 4) = 0
x = 6
x = -4
(c) y = 8, -2
(y - 2)^2 - 2(y - 2) - 24 = 0
(y^2 - 4y + 4) - 2y + 4 - 24 = 0
y^2 - 6y - 16 = 0
(y - 8)(y + 2) = 0
y = 8
y = -2
Hope this helps! :)