HELP!!!!! Срочно надо! 83!

82. 1)
$(a - 1) {(a + 3)}^{2} = (a - 1)( {a}^{2} + 6a + 9) = {a}^{3} + 6 {a}^{2} + 9a - {a}^{2} - 6a - 9 = {a}^{3} + 5 {a}^{2} + 3a - 9$
2)
${( x - 4)}^{2} (x + 2) = ( {x}^{2} - 8x + 16)(x + 2) = {x}^{3} - 8 {x}^{2} + 16x + 2 {x}^{2} - 16x + 32 = {x}^{3} - 6 {x}^{2} + 32$
83.
$\frac{ {x}^{2} + {y}^{2} - {z}^{2} - 2xy}{ {x}^{2} - {y}^{2} + {z}^{2} + 2xz} = \frac{ {(x - y)}^{2} - {z}^{2} }{ {(x + z)}^{2} - {y}^{2} } = \frac{(x - y + z)(x - y - z)}{(x + z + y)(x + z - y)} = \frac{x - y - z}{x + y + z}$