Ответ:

Объяснение:

1)

[(a+3)/(a-3)+(a-3)/(a+3)]: (3a²+27)/(9-a²)=

=[(a+3)²+(a-3)²]/( a²-9) *-(a²+9)/3(a²+9) =

=[(a²+6a+9+a²-6a+9)/(a²-9) *(-1/3)=(2a²+18)/(a²-9) *(-1/3)=

=-2(a²+9)/3(a²-9)

2)

(5x  -10x/(x+1)  : (15x-15)/(4x+4)= [5x(x+1)-10x)]/(x+1) * 4(x+1)/3(x-1)=

=(5x²+5x-10x) *4/3(x-1)=( 5x²-5x)* 4/3(x-1)=5x(x-1) *4/3(x-1)=

=20x/3