Question

My teacher найдите значение выражения (1/9а+1/5а)•а/8 при а=-9

Answer 1

( -1/81-1/45)·(-9/8)= (-5/81-1/45)·(-9/8)= (-86/405)·(-9/8)=86·9/405·8=43/180

Answer 2

$( \frac{1}{9}a + \frac{1}{5}a) \times \frac{a}{8} = \frac{5a + 9a}{40} \times \frac{a}{8} = \\ = \frac{14a}{40} \times \frac{a}{8} = \frac{7 {a}^{2} }{160} =$

$= \frac{7 {a}^{2} }{160} = \frac{7 \times {( - 9)}^{2} }{160} = \frac{7 \times 81 }{160} = \\ = \frac{567}{160} = 3 \frac{87}{160} .$