x2 + 4x = 0 ⇒ x(x + 4) = 0 ⇒ x = 0 or x = -4
x2 - 4x + 4 = 0 (x - 2)(x - 2) = 0 x = 2
x2 + 12x - 64 = 0 ∴ (x + 16)(x - 4) = 0 ∴ x ∈ {4, -16}
x2+6x-40 = 0 (x+10)(x-4) = 0 x = 4 or x = -10
x2+4x+4 = 25 x2+4x+4-25 = 0 x2+4x-21 = 0 (x+7)(x-3) = 0 x = -7 or x = 3
x2 + 4x = 0 ⇒ x(x + 4) = 0 ⇒ x = 0 or x = -4
x2 - 4x + 4 = 0 (x - 2)(x - 2) = 0 x = 2
x2 + 12x - 64 = 0 ∴ (x + 16)(x - 4) = 0 ∴ x ∈ {4, -16}
x2 - 4x = 0 x(x - 4) = 0 so either x = 0 or x - 4 = 0 that is, x = 0 or x = 4.
x2+6x-40 = 0 (x+10)(x-4) = 0 x = 4 or x = -10
x2+4x+4 = 25 x2+4x+4-25 = 0 x2+4x-21 = 0 (x+7)(x-3) = 0 x = -7 or x = 3
-x2 + 5x - 4 = 0. Then, x2 - 5x + 4 = (x - 4)(x - 1) = 0; whence, x = 1 or 4. Checking, -1 + 5 - 4 = 0; and -16 + 20 - 4 = 0.
x2 + 8x - 6 = 0 x2 + 8x + 16 = 22 (x + 4)2 = 22 x + 4 = ± √22 x = -4 ± √22
x2=9x-20 x2-9x+20=0 Factor: (x-4)(x-5)=0 x={4,5}
x2 23x equals 0
x2+8x+9 = -7 x2+8x+9+7 = 0 x2+8x+16 = 0 (x+4)(x+4) = 0 Therefore: x = -4 and also x = -4 (they both have equal roots)
x2 + 13x + 36 = 0 so (x+4)(x+9) = 0 so that x = -4 or x = -9