a)2xy.3x²y³=6x³$y^{4}$
b)x.(x²-2x+5)=x³-2x²+5x
c)(3x²-6x):3x=(x(3x-6)):3x=x-6
d)(x²-2x+1):(x-1)=(x-1)²:(x-1)=x-1
2:
a)5x²y-10xy²=5xy(x-2y)
b)3(x+3)-x²+9=3(x+3)+(x-3)(x+3)=(x+3)(3x-9)
c)x²-y²+xz-yz=(x+y)(x-y)+z(x-y)=(x-y)(x+y+z)
3:
a)đk:x$\neq$ 2;x$\neq$ -2
b)pt⇔(x²-x(x+2)+2(x-2))/(x²-4)=(x²-x²-2x+2x-4)/(x²-4)=$\frac{-4}{x²-4}$
c)thay x=1;pt⇔$\frac{-4}{1-4}$ =$\frac{4}{3}$
4:bạn tự cm nhé