Question

$(x + y) {}^{2}$

Answer 1

$(x + y) {}^{2} = x {}^{2} + 2xy + y {}^{2}$
Hope it helps! :)

Answer 2

$(x + y) {}^{2} = (x + y)(x + y) \\ = x(x + y) + y(x + y) \\ = x {}^{2} + xy + xy + y {}^{2} \\ = x {}^{2} + 2xy + y {}^{2}$