Đáp án:
Giải thích các bước giải:
Bài 1:
a) `x^2+2x=x(x+2)`
b) `xyz+x^2 y^3 z+xyz^2=xyz(1+xy^2+z)`
c) `3(x-y)+y(y-x)=3(x-y)-y(x-y)=(3-y)(x-y)`
d) `xy(x+y)-5x-5y=xy(x+y)-5(x+y)=(xy-5)(x+y)`
Bài 2:
`x(x-3)(x+3)-(x+2)(x^2-2x+4)+x(x+7)=0`
`⇔ x(x^2-9)-(x^3+8)+x^2+7x=0`
`⇔ x^3-9x-x^3-8+x^2+7x=0`
`⇔ x^3-x^3+x^2-9x+7x-8=0`
`⇔ x^2-2x-8=0`
`⇔ x^2+2x-4x-8=0`
`⇔ (x+2)(x-4)=0`
`⇔` \(\left[ \begin{array}{l}x=-2\\x=4\end{array} \right.\)
vậy `S={-2;4}`
