178a
1)0,5(b-3)/0,5(b²-3b+9) -(6b-18)/(b+3)(b²-3b+9)=(b²-9-6b+18)/(b+3)(b²-3b+9)=
=(b²-6b+9)/(b+3)(b²-3b+9)=(b-3)²/(b+3)(b²-3b+9)
2)(b-3)²/(b+3)(b²-3b+9): (b-3)/0,8(b³+27)=(b-3)²/(b³+27)*0,8(b³+27)/(b-3)=
=0,8(b-3)=0,8b-2,4
178б
1)2a/(a+2) -2a/3(a-2) +8a/(a-2)(a+2)=(6a²-12a-2a²-4a-24a)/3(a-2)(a+2)=
=(4a²+8a)/3(a-2)(a+2)=4a(a+2)/3(a-2)(a+2)=4a/3(a-2)
2)4a/3(a-2)*0,5(a-2)/2,5(a-0,8)=8/(3a-2,4)