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