а)((9y(X+y)-9xy)/X(X+y))*(X+y)^2/9y^2=(9y^2)/(x(X+y)) * (X+y)^2/9y^2=(X+y)/X
b)(4x(x-2)-12x)/x-2 / (X(x-2)-8x-25)/(x-2)=(4x^2-8x-12x)/(x^2-2x-8x-25)=4x^2-20x/x^2-10x-25=4x(x-5)/(x-5)^2=4x/x-5
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