Question

(a - b)(x -1) + (x + 1)(a + b) = 0

Answer 1

(a - b)(x -1) + (x + 1)(a + b) = 0
ax - a - bx + b + ax + bx + a + b = 0

2ax + 2b = 0

ax =  -b

$x = -\frac{b}{a}$