(3-x)=+2(x-3)+=3 (2x+1)²=13+4x² (6x-1)(1+6x)-4x(9x+3)=-145 подробней

=
- 3 + x = 2x - 6 + 3
х - 2х = - 6 + 3 +3
- х = 0
  х = 0

(2х + 1)^2 = 13 + 4x^2
4x^2 + 4x + 1 = 13 + 4x^2
4x^2 - 4x^2 + 4x = 13 - 1
4x = 12
x = 3

=
6х - 1 + 36х^2 - 6x - 36x^2 - 12x = - 145
36x^2 - 36x^2 -12x = - 145 +1 
-12x = - 144
12x = 144
x = 12