Question

$(x + 3y) {}^{2}$

Answer 1

$(x + 3y) {}^{2} = {(x)}^{2} + (3y) {}^{2} + 2 \times x \times 3y \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = {x}^{2} + {9y}^{2} + 6xy$

Answer 2

Hope it will help u..