1)(x-3)/(3x+6) - (x-6)/(x+2)=(x-3)/3(x+2) - (x-6)/(x+2)=
=(x-3-3x+18)/(3(x+2)=(-2x+15)/(3x+6)
2)(m+4)/(5m-10) + (3-m)/(4m-8)=(m+4)/5(m-2) + (3-m)/4(m-2)=
=(4(m+4)+5(3-m))/20(m-2)=(4m+16+15-5m)/20(m-2)=(-m+31)/(20m-40
3)(y+6)/(y-6) - (y+2)/y+6)=((y+6)(y+6)-(y+2)(y-6))/((y-6)(y+6)=
=(y²+12y+36-y²+6y-2y+12)/(y²-36)=(16y+48)/(y²-36)
4)3x/(4x-4) + 5x/(7-7x)=3x/4(x-1) + 5x/7(x-1)=(7.3x+4.5x)/28(x-1)=
=(21x+20x)/(28x-28)
5)2b/(2b+c) - 4b²/(4b²+4bc+c²)=2b/(2b+c) - 4b²/(2b+c)²=
=(2b(2b+c) - 4b²)/(2b+c)²=(4b²+2bc-4b²)/(2b+c)²=2bc/(2b+c)²
6)2/(a²-9) - 1/(a²+3a)= 2/(a+3)(a-3) - 1/a(a+3)=(2a-a+3)/a(a+3)(a-3)=
=(a+3)/a(a+3)(a-3)=1/a(a+3) , a≠0,a≠3,a≠-3