Решите эти 2 примера, 7 класс. пожалуйста

Решите задачу:

$1)\; \; \frac{1}{1-\frac{1}{1-\frac{1}{x+1}}} = \frac{1}{1-\frac{x+1}{x+1-1}} = \frac{1}{1-\frac{x+1}{x}} = \frac{x}{x-x-1}=\frac{x}{-1}=-x$

$2)\; \; \frac{1}{(x-y)(x-3)}+\frac{1}{(y-3)(y-x)} +\frac{1}{(3-x)(3-y)} =\\\\= \frac{1}{(x-y)(x-3)} -\frac{1}{(y-3)(x-y)} +\frac{1}{(x-3)(y-3)} =\\\\=\frac{(y-3)-(x-3)+(x-y)}{(x-y)(x-3)(y-3)} = \frac{y-3-x+3+x-y}{(x-y)(x-3)(y-3)} = \frac{0}{(x-y)(x-3)(y-3)} =0$