Ответ №1
1)(x+y)/7 : (x+y)/7a = (x+y)/7 . 7a/(x+y)=(x+y).7a/7(x+y)=a
a≠0, x≠-y
Formula: a/b : c/d= ad/bc
2)(2a/3b)³= (2a)³/(3b)³=2³a³/3³b³=8a³/27b³, b≠0
3)(x²-y²)/(10x²y) . (25xy²)/(x+y)=(x+y)(x-y).25xy²/10x²y(x+y)=
=(x-y).25xy²/10x²y=5y(x-y)/2x , x≠0,y≠0,x≠-y
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