Question

Алгебра
Дроби

СРОЧНО

Answer 1

$\displaystyle\tt \ \ \ a-\frac{a^3-15a-4}{a^2-16}=\frac{a(a^2-16)-(a^3-15a-4)}{a^2-16}=\\\\\\=\frac{a^3-16a-a^3+15a+4}{(a-4)(a+4)}=\frac{-a+4}{(a-4)(a+4)}=\\\\\\ =\frac{-(a-4)}{(a-4)(a+4)}=\frac{-1}{a+4}$

при а = -4,5

$\displaystyle\tt \frac{-1}{a+4}=\frac{-1}{-4,5+4}=\frac{-1}{-0,5}=2$