Answer:
see explanation
Step-by-step explanation:
Given
(a + b - 2)(a - b + 2)
Each term in the second factor is multiplied by each term in the first factor, that is
a(a - b + 2) + b(a - b + 2) - 2(a - b + 2) ← distribute the parenthesis
= a² - ab + 2a + ab - b² + 2b - 2a + 2b - 4 ← collect like terms
= a² - b² +4b - 4
