Question

how to expand (x+y-a-b)²​

Answer 1

we will make two pairs and enclose yhem in brackets

[(x+y) - (a - b)]² = (x+y)² + (a - b)² - 2 x (x+y) x (a - b)

= x² +y² + 2xy + a² + b² + 2ab - 2[xa - xb + ya - yb]

= x² + y² + 2xy + a² + b² + 2ab -2ax +2xb -2ay + 2by

so, hope , it helps you