Выбери верный ответ

Выполни действия:

1. \(\dfrac{3x}{4x-4}+\dfrac{5x}{7-7x}=\) [ \(\frac {x}{28(x-1)}\) | \(\frac {x}{x-1}\) | \(\frac{1}{x-1}\) | \(\frac {1}{xy}\) ];
2. \(\dfrac{2b}{2b+c}-\dfrac{4b^2}{4b^2+4bc+c^2}=\) [ \(\frac {2bc}{(2b+c)^2}\) | \(\frac {bc}{(2b+c)^2}\) | \(\frac{c}{2b+c}\) | \(\frac {1}{2b+c}\) ];
3. \(\dfrac{2}{a^2-9}-\dfrac{1}{a^2+3a}=\) [ \(-\frac {2}{a-3}\) | \(\frac 1a\) | \(\frac {1}{a(a-3)}\) | \(\frac {1}{a+3}\) ].