Помогите с выполнением заданий 4,5,6. Спасибо

Решите задачу:

$1) \frac{2x+1}{12x^{2}y} +\frac{2-3y}{18xy^{2}}=\frac{6xy+3y+4x-6xy}{36x^{2}y^{2}}=\frac{4x+3y}{36x^{2}y^{2}} \\\\2) \frac{a+1}{2a(a-1)}-\frac{a-1}{2a(a+1)}=\frac{(a+1)(a+1)-(a-1)(a-1)}{2a(a+1)(a-1)}=\frac{a^{2}+2a+1-a^{2}+2a-1}{2a(a^{2}-1)}=\frac{4a}{2a(a^{2}-1)}=\frac{2}{a^{2}-1}\\\\3) -\frac{36}{x^{2}-6x}+\frac{x}{x-6} -\frac{6}{x}=-\frac{36}{x(x-6)}+\frac{x}{x-6} -\frac{6}{x}=\frac{-36+x*x-6(x-6)}{x(x-6)}=\frac{-36+x^{2}-6x+36}{x^{2}-6x}=\frac{x^{2}-6x}{x^{2}-6x}=1$