X=4
Explanation
First subtract 4x^2 + 6x from both sides of the equation
X^2 - 8x + 16 = 0
Then let’s factorice the equation using the middle-term break:
x^2 - 4x - 4x + 16 = 0
x (x - 4) - 4 (x - 4) = 0
(x - 4) (x - 4) = 0
(x - 4) ^2 = 0
x = 0
Therefore the solution to the equation is x = 4