(2*x+3)*(2*x+3)-4*(x-1)*(x+1)=49.
(4*x²+9+6*x+6*x)-4*(x²-1)=49.
4*x²-4*x²+4+12*x+9=49.
12*x+13=49.
12*x=49-13.
12*x=36.
x=36:12.
x=3.
ответ:3.
2 вариант
(2x+3)*(2x+3)-4(x-1)(x+1)=49
4х^2+6x+6x+9-4(x^2-1)=49
4х^2+12x+9-4(x^2-1)=49
12x+9+4=49
12x=49-4-9
12x=36
x=3
