Question

Factor by grouping.
x2 + 8x + xy + 8y

Answer 1

= x(x + 8) - y(x + 8)
= (x - y)(x + 8)

Answer 2

Don't you see that y is a stranger. So group it -y(x+8)
The balance just happens to be x(x+8)
So you have these two terms. Take the common factor out.
(x+8) (x-y) now that's the answer. Easy ...