Question

найдите значение выражения при 14/7b-b^2-2/b при b=-3

Answer 1

$\frac{14}{7b-b^{2} }-\frac{2}{b}=\frac{14}{b(7-b)}-\frac{2}{b} =\frac{14-2(7-b)}{b(7-b)}=\frac{14-14+2b}{b(7-b)}=\frac{2b}{b(7-b)}=\boxed{\frac{2}{7-b}} \\\\b=-3\\\\\frac{2}{7-b}=\frac{2}{7-(-3)}=\frac{2}{7+3}=\boxed{0,2}$