Выбери верные ответы

1. \(\textcolor{white}{\boxed{\textcolor{black}{\dfrac{7a}{a-4}+\dfrac{5a}{4-a}=}}}\) [ \(\frac{12}{a-4}\) | \(\frac{2a}{a-4}\) | \(\frac{2a}{4-a}\) ]
2. \(\textcolor{white}{\boxed{\textcolor{black}{\dfrac{2-3b}{3b-4}+\dfrac{1-3b}{4-3b}=}}}\) [ \(\frac{3}{3b-4}\) | \(\frac{1}{3b-4}\) | \(\frac{3b}{3b-4}\) ]
3. \(\textcolor{white}{\boxed{\textcolor{black}{\dfrac{1}{y^3-5y}-\dfrac{1}{y^2-5}=}}}\) [ \(\frac{1-y}{y^3-5y}\) | \(0\) | \(\frac{y}{y^2-5}\) ]