Решите плиз я дам 10 баллов

2)Б
3)(х+5)²-х(3х-10)=х²+25+10х-3х²+10х=-2х²+25+20х
4)4х²-25у²=(2х+5у)(2х-5у)
5) $\frac{y}{ x^{2} -xy} * x^{2} = \frac{y}{x(x-y)} * x^{2} = \frac{xy}{x-y}$
6) $\frac{a}{a-2} - \frac{a}{a+2} = \frac{a(a+2)-a(a-2)}{(a-2)(a+2)} = \frac{a(a+2-a+2)}{ a^{2}-4 } = \frac{4a}{a^{2}-4 }$
7) $\frac{2x}{ x^{2} -4} - \frac{2x}{ x^{2} -4} :( \frac{x+1}{2(x-1)} - \frac{2}{2(x-1)} =\frac{2x}{ x^{2} -4} - \frac{2x}{ x^{2} -4} : \frac{x-1}{2(x-1)} =$ $\frac{2x}{ x^{2} -4} - \frac{2x}{ x^{2} -4} *2=\frac{2x}{ x^{2} -4} - \frac{4x}{ x^{2} -4} =- \frac{2x}{ x^{2} -4}$