1)
x^2 -5x + 4 = 0
(x -4)(x - 1) = 0
x - 4 = 0; x = 4
x - 1 = 0; x = 1
answer
x = 1 and x =4
2)
x^2 -7x + 12 = 0
(x-3)(x-4) = 0
x - 3 = 0; x = 3
x - 4 = 0; x = 4
answer
x = 3 and x =4
3)
x^2 + 7x + 6 = 12x
x^2 - 5x + 6 = 0
(x - 3)(x - 2) = 0
x - 3 = 0; x = 3
x - 2 = 0; x = 2
answer
x = 3 and x = 2
4)
15 + 2x = x^2
x^2 - 2x - 15 = 0
(x - 5)(x+ 3) = 0
x - 5 = 0; x = 5
x + 3 = 0; x = -3
answer
x = -3 and x = 5