Question

298 помогите пожалуйста.
Только подробно распишите.

Answer 1

$1) \: \: \: 2 {a}^{3} + 3ab - {b}^{2} - 6{a}^{3} - 7ab + 2 {b}^{2} = - 4 {a}^{3} - 4ab + {b}^{2} = - 4 \times {2}^{3} - 4 \times 2 \times ( - 6) + {( - 6)}^{2} = - 4 \times 8 + 48 + 36 = - 32 + 84 = 52$
$2) \: \: \: mn - 6m {n}^{2} - 8mn - 6m {n}^{2} = - 7mn - 12m {n}^{2} = - 7 \times 0.5 \times ( - 2) - 12 \times 0.5 \times {( - 2)}^{2} = 7 - 24 = - 17$
$3) \: \: \: 10x {y}^{2} - 12 {x}^{2} y + 9 {x}^{2} y - 9x {y}^{2} = x {y}^{2} - 3 {x}^{2} y = \frac{1}{3} \times {9}^{2} - 3 \times {( \frac{1}{3}) }^{2} \times 9 = \frac{( {3}^{2}) ^{2} }{3} - \frac{3 \times 9}{9} = {3}^{3} - 3 = 24$