(2х-3)(2х+3)-х2=12х-69+3х2
(2х-3)(2х+3)-х²=12х-69+3х²
4x²-9-x²=12x-69+3x²
12x=60
x=5
(2x-3)(2x+3)-x^2=12x-69-3x^2
4x^2-9-x^2-12x+69+3x^2=0
-12x+60=0
-12x=-60
x=-60\(-12)
Ответ:x=5