120. Представьте в виде рациональной дроби выражения: а) \(\left(\frac{a}{a+2}+1\right)\cdot\frac{a+2}{4a^2}\); б) \(\left(\frac{2b}{1-b}-b\right):\frac{3b+3}{b-1}\); в) \(\frac{3x}{x^2-1}:\left(1+\frac{1}{x-1}\right)\); г) \(\frac{2y-12}{y^2-25}\cdot\left(y+\frac{y}{y-6}\right)\); д) \(\left(a-x+\frac{x^2}{a+x}\right)\cdot\frac{a-x}{a}\); е) \(\left(2b+y-\frac{3y^2}{2b-y}\right)\cdot\frac{4b-3y}{b^2+by}\).

\(\left(\frac{a}{a+2}+1\right)\cdot\frac{a+2}{4a^2}=\frac{2a+2}{a+2}\cdot\frac{a+2}{4a^2}=\frac{a+1}{2a^2}.\)

\(\left(\frac{2b}{1-b}-b\right):\frac{3b+3}{b-1}=\frac{b(b+1)}{1-b}\cdot\frac{b-1}{3(b+1)}=-\frac{b}{3}.\)

\(\frac{3x}{x^2-1}:\left(1+\frac{1}{x-1}\right)=\frac{3x}{(x-1)(x+1)}:\frac{x}{x-1}=\frac{3}{x+1}.\)

\(\frac{2y-12}{y^2-25}\cdot\left(y+\frac{y}{y-6}\right)=\frac{2(y-6)}{(y-5)(y+5)}\cdot\frac{y(y-5)}{y-6}=\frac{2y}{y+5}.\)

\(\left(a-x+\frac{x^2}{a+x}\right)\cdot\frac{a-x}{a}=\frac{a^2}{a+x}\cdot\frac{a-x}{a}=\frac{a(a-x)}{a+x}.\)

\(\left(2b+y-\frac{3y^2}{2b-y}\right)\cdot\frac{4b-3y}{b^2+by}=\frac{4(b-y)(b+y)}{2b-y}\cdot\frac{4b-3y}{b(b+y)}=\frac{4(b-y)(4b-3y)}{b(2b-y)}.\)