Решите пожалуйста очень нужно. Номера 142 144 146

№142.
$( \frac{c}{b-c} - \frac{c}{b} ): \frac{c ^{2} }{b ^{2} } =(\frac{bc}{b(b-c)} - \frac{bc-c ^{2} }{b(b-c)} )* \frac{b ^{2} }{c ^{2} } =\frac{bc-bc+c ^{2} }{b(b-c)} *\frac{b ^{2} }{c ^{2} } = \frac{ c^{2} b^{2} }{b(b-c)*c ^{2} } = \frac{b}{b-c}$
№144.
$( \frac{a}{b}- \frac{b}{a})* \frac{b}{a-b}= \frac{a ^{2}-b ^{2} }{ab}* \frac{b}{a-b}= \frac{(a-b)(a+b)*b}{ab*(a-b)} = \frac{a+b}{a}$
№146.
$\frac{c-3}{c} - \frac{ c^{2} -9}{c} *\frac{1}{c-3}= \frac{c-3}{c} - \frac{ (c-3)(c+3)}{c} *\frac{1}{c-3}=\frac{c-3}{c} - \frac{ (c-3)(c+3)}{c*(c-3)} =$ $\frac{c-3}{c} - \frac{ c+3}{c} =\frac{c-3-c-3}{c} =\frac{-6}{c}$