Question

сделайте побыстрее пж​

Answer 1

1)

$12 {a}^{2} - 12ab - 7a + 7b = 12a(a - b) - 7(a - b) = (12a - 7)(a - b)$

Если a = 1 1/6, b = 2/3, то

$(12a - 7)(a - b) = \\ (12 \times 1 \frac{1}{6} - 7 )(1 \frac{1}{6} - \frac{2}{3} ) = \\ (12 \times \frac{6 \times 1 + 1}{6} - 7)( \frac{6 \times 1 + 1}{6} - \frac{2}{3} ) = \\ (12 \times \frac{7}{6} - 7)( \frac{7}{6} - \frac{2}{3} ) = \\ (14 - 7)( \frac{7 - 2 \times 2}{6} ) = \\ 7 \times \frac{1}{2} = \frac{7}{2} = 3 \frac{1}{2} = 3.5$

2)

$5 {a}^{3} - {a}^{2} - 5a + 1 = (5 {a}^{3} - 5a) - ( {a}^{2} - 1) = 5a( {a}^{2} - 1) - ( {a}^{2} - 1) = (5a - 1)( {a}^{2} - 1)$

Если a = 0,2, то

$(5a - 1)( {a}^{2} - 1) = (5 \times 0.2 - 1)( {(0.2)}^{2} - 1) = (1 - 1)(0.04 - 1) = 0 \times ( - 0.96) = 0$