Условие:
Упростите выражение:
1) ((a+3)/(a-3)+(a-3)/(a+3))∶(3a^2+27)/(9-a^2);
2) (5x-10x/(x+1))∶(15x-15)/(4x+4);
3)3a/(a-4)-(a+2)/(5a-20)*240/(a^2+2a);
4) (8b/(b+7)-15b/(b^2+14b+49))∶(8b+41)/(b^2-49)+(7b-49)/(b+7);
5) ((a-b)/(a^2+ab)-a/(ab+b^2))∶(b^2/(a^3-ab^2)+1/(a+b));
6) (x^2+5x)/(x-5)^2∶(5/(x+5)+(x^2+25)/(x^2-25)-5/(5-x)).