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Выполни действия.

1. \(\dfrac{5y}{2y-10}+\dfrac{3y}{15-3y}=\) [ \(\frac {3y}{2(y-5)}\) | \(\frac {y}{y-5}\) | \(\frac{1}{y+5}\) | \(\frac {1}{y}\) ];
2. \(\dfrac{5x}{5x+y}-\dfrac{25x^2}{25x^2+10xy+y^2}=\) [ \(\frac {5xy}{(5x+y)^2}\) | \(\frac {xy}{(5x+y)^2}\) | \(\frac{y}{5x+y}\) | \(\frac {1}{5x-y}\) ];
3. \(\dfrac{8}{x^2-49}-\dfrac{4}{x^2+7x}=\) [ \(-\frac {2}{x-7}\) | \(\frac 1x\) | \(\frac {4}{x(x-7)}\) | \(\frac {1}{x+7}\) ].