Question

под а и б пж быстро нужнл

Answer 1

$frac{15 x^{3} y^{2} }{14 a^{2} b^{2} } : frac{20 x^{2} y^{3} }{21 a^{2} b}= frac{15 x^{3} y^{2} }{14 a^{2} b^{2} }* frac{21 a^{2} b}{20 x^{2} y^{3} }= frac{15x}{14b}* frac{21}{20y}= frac{9x}{8by} \ \ frac{z+y}{ z^{2} -yz} * frac{z}{z+y} = frac{z}{ z^{2}-y } = frac{z}{z(z-y)} = frac{1}{z-y}$