Решение №4

1. a) $$\frac{2m}{m-n} + \frac{2n}{n-m} = \frac{2m}{m-n} - \frac{2n}{m-n} = \frac{2m - 2n}{m-n} = \frac{2(m-n)}{m-n} = 2$$
2. б) $$\frac{x^2}{x+y} - \frac{xy}{-y-x} = \frac{x^2}{x+y} + \frac{xy}{x+y} = \frac{x^2 + xy}{x+y} = \frac{x(x+y)}{x+y} = x$$
3. в) $$\frac{3c}{c+d} - \frac{3d}{-d-c} = \frac{3c}{c+d} + \frac{3d}{c+d} = \frac{3c + 3d}{c+d} = \frac{3(c+d)}{c+d} = 3$$
4. г) $$\frac{pq}{p-q} + \frac{q^2}{q-p} = \frac{pq}{p-q} - \frac{q^2}{p-q} = \frac{pq - q^2}{p-q} = \frac{q(p-q)}{p-q} = q$$