Question

Please solve question no 18 and 10

Answer 1

$2(ab \: + cd) - {a}^{2} - {b}^{2} + {c}^{2} + {d}^{2} \\ 2ab + 2cd - (a - b - c -d {)}^{2} \\ 2(a + b)(c + d) - (a - b {)}^{2} - (c - d {)}^{2}$

it's your solution i hope u understand