(3x+1)•(5x-1)=(5x+2)(3x-4)-7x
15х² +5х - 3х - 1 = 15х² + 6х - 20х - 8 - 7х
2х-1 = -21х -8
23х = -7
х = -7/23
4x • 4x = 7x • 0 - 7x
16x = 7x
x = -16 + 7x
x = -9x
Вроде так
(3x+1)•(5x-1)=(5x+2)(3x-4)-7x
15х² +5х - 3х - 1 = 15х² + 6х - 20х - 8 - 7х
2х-1 = -21х -8
23х = -7
х = -7/23