Question

$(x -y) frac{x + y}{ x - y}$

Answer 1

$(x-y) frac{x+y}{x-y} = frac{x-y}{1} * frac{x+y}{x-y} = frac{(x-y)(x+y)}{1*(x-y)} = frac{1*(x+y)}{1*1} = frac{x+y}{1} = x+y$