Ответ:

Объяснение:

1) (1 -1/a)² ÷(a-1)/(3a²)=(a-1)²/a² ·(3a²)/(a-1)=3(a-1)=3a-3

2) (1 +y/x) ÷(y/x -1)=(x+y)/x ÷(y-x)/x=(x+y)/x ·x/(y-x)=(x+y)/(y-x)=-(x+y)/(x-y)

3) a/(1-b) -(a²+ab)/(b²-1) ·(b+1)/(a+b)=-a/(b-1) -(a(a+b))/((b-1)(b+1)) ·(b+1)/(a+b)=-a/(b-1) -a/(b-1)=-(2a)/(b-1)

4) a/(a-3) ÷(a²+2a)/(a²-9) -a/(a+2)=a/(a-3) ·((a-3)(a+3))/(a(a+2)) -a/(a+2)=(a+3)/(a+2) -a/(a+2)=(a+3-a)/(a+2)=3/(a+2)