Question

x(x + 4) + x(x + 2) = 2x2 + 12

Answer 1

$x(x + 4) + x(x + 2) = 2 {x}^{2} + 12 \\ {x}^{2} + 4x + {x}^{2} + 2x - 2 {x}^{2} - 12 = 0 \\ 6x - 12 = 0 \\ 6x = 12 \\ x = \frac{12}{6} \\ x = 2$