1)3a-4ax+2-11a+4ax=2-8a
b)a²-18a+81-81-2a=a²-20a=a(a-20)
c)x(2x-1)²-2(x+1)(x²-x+1)=x(4x²-4x+1)-2(x³+1)=2x³-4x²-1
2)2a+b+2a²+ab=2a(a+1)+b(a+1)=(a+1)(2a+b)
b)3x²-12=3(x²-4)=3(x-2)(x+2)
c)x²-4x+4-y²-6y-9=(x-2)²-(y²+6y+9)=(x-2)²-(y+3)²=(x-y-5)(x+y+1)
3)a) (5y+4y-8)/20=(9y-8)/20
b)4a/3(a-2) -3a/4(a-2)=7a/12(a-2)
c)(a-3)(a+3)/(a+3)²:(-)(a-3)/(a+3)=(a+3)(a-3)/(a+3)²·(-)(a+3)/(a-3)=-1
