Question

помогите пожалуйста 499 (3,4) решить, я не могу

Answer 1

3) $frac{(c-d)(c+d)-2c ^{2}}{c(c-d)} * frac{-(c-d)}{c^{2} + d^{2} } = frac{c ^{2} -d ^{2} -2c ^{2}}{c(c-d)} * frac{-(c-d)}{c^{2} + d^{2} }=- frac{-c ^{2}-d ^{2} }{c} * frac{1}{c^{2} + d^{2} }=$$frac{c ^{2} +d ^{2} }{c} * frac{1}{c^{2} + d^{2} }= frac{1}{c}$
4) $frac{2c ^{2} +(d-c)(d+c)}{c(c+d)}* frac{c+d}{ c^{2}+ d^{2} } = frac{2c ^{2} + d^{2}- c^{2} }{c(c ^{2} +d ^{2} )}= frac{c ^{2} + d^{2} }{c(c ^{2} +d ^{2} )}= frac{1}{c}$