If you would like to solve the equation 2 * x^2 + 8 * x = x^2 - 16, you can calculate this using the following steps:
2 * x^2 + 8 * x = x^2 - 16
2 * x^2 - x^2 + 8 * x + 16 = 0
x^2 + 8 * x + 16 = 0
(x + 4) * (x + 4) = 0
x = - 4
The correct result would be x = - 4.