>>596
x^2−36=0
(x-6)(x+6) = 0
x=±6

x^2−x−20=0
(x-5)(x+4)=0
x = 5, -4

x^2−4x=0
x(x-4) = 0
x = 0, 4

2x^2−7x+6=0
(2x-3)(x-2) = 0
x = (3/2), 2

x^2−5x+6=0
(x-2)(x-3) = 0
x = 2,3

x^2+7x=0
x(x+7) = 0
x = 0, -7