Question

If a+b=−2a + b = -2a+b=−2a+b= -2 and x+y =−2 what is 4x+5a+4y+5b?

Answer 1

$a + b = -2\ and\ x + y = -2\\\\4x + 5a + 4y + 5b = (4x + 4y) + (5a + 5b) = 4(\underbrace{x + y}_{=-2}) + 5(\underbrace{a + b}_{=-2})\\\\=4(-2)+5(-2)=-8+(-10)=-18$