Помогите первое и второе

1.
$\frac{(a^{6}b^{9})^{ \frac{2}{3} }}{b^{10}}= \frac{a^{4}b^{6}}{b^{10}}= \frac{a^{4}}{b^{4}}$

при а=5, b=10
$\frac{5^{4}}{10^{4}} = \frac{5^{4}}{2^{4}*5^{4}} = \frac{1}{2^{4}}= \frac{1}{16}$

2.
$(\frac{c}{c-2}- \frac{c}{c+2} - \frac{c^{2} +4}{4-c^{2} } )* \frac{(2-c)^{2}}{2c- c^{2} }=(- \frac{c}{2-c} - \frac{c}{c+2} - \frac{c^{2} +4}{(2-c)(2+c) } )* \frac{(2-c)(2-c)}{c(2+ c)}= \\ \\ \frac{-c(2+c)-c(2-c)- c^{2} - 4}{(2-c)(2+c)}* \frac{(2-c)(2-c)}{c(2+ c)}= \frac{-2c- c^{2}-2c+c^{2}-c^{2} -4 }{2+c} * \frac{2-c}{c(2+c)}= \\ \\ \frac{- c^{2} -4c-4}{2+c} * \frac{2-c}{c(2+c)}= \frac{-(c+2)(c+2)(2-c)}{c(2+c)(2+c)} = \frac{-(2-c)}{c} = \frac{c-2}{c}$