A
1)=(4b²+21-12b-12)/2(b+1)=(4b²-12b+9)/2(b+1)=(2b-3)²/2(b+1)
2)=[2b(a+2)-3(a+2)]/2b(1+b)=(a+2)(2b-3)/2b(1+b)
3)(a+2)(2b-3)/2b(1+b) : (2b-3)²/2(b+1)=(a+2)(2b-3)/2b(1+b) * (b+1)/(2b-3)²=
=(a+2)/(2b²-3b)
б
1)=(x²+x+1-x²+1)/(x³-1)=(x+2)/(x³-1)
2)=(x³-1+9)/(x³-1)=(x³+8)/(x³-1)
3)(x+2)/(x³-1) : (x³+8)/(x³-1)=(x+2)/(x³-1) * (x³-1)/(x+2)(x²-2x+4)=1/(x²-2x+4)