bài 1:
`a) (x+2)^2-(x-2)(x+2)=0`
`<=> (x+2)(x+2-x+2)=0`
`<=> 4(x+2)=0`
`<=>x+2=0`
`<=> x=-2`
`b) (3x-1)(2x+7)-(x+1)(6x-5)=16`
`<=> 6x^2+21x-2x-7-(6x^2-5x+6x-5)-16=0`
`<=> 6x^2+19x-7-6x^2-x+5-16=0`
`<=> 18x-18=0`
`<=> 18(x-1)=0`
`<=> x-1=0`
`<=> x=1`
bài 2:
`a) 5x^3-10x^2y+5xy^2`
`=5x(x^2-2xy+y^2)`
`=5x(x-y)^2`
`b) 5x^2-10xy^2`
`=5x(x-2y^2)`
`c) 3(x+3)-x^2+9`
`=3(x+3)-(x^2-9)`
`=3(x+3)-(x-3)(x+3)`
`=(x+3)(3-x+3)`
`=(x+3)(6-x)`
`d) x^2-y^2+xz-yz`
`=(x-y)(x+y)+z(x-y)`
`=(x-y)(x+y+z)`
`e) x^2+4x`
`=x(x+4)`
`g) x^3-2x^2+5x-10`
`=x(x-2)+5(x-2)`
`=(x-2)(x+5)`
`h) 2xy+2x=2x(y+1)`
`i) x^2-6x+xy-6y`
`=x(x-6)+y(x-6)`
`=(x-6)(x+y)`
`k) x^2-xy+x-y`
`=x(x-y)+(x-y)`
`=(x-y)(x+1)`
`l) x^2-y^2-5x-5y`
`=(x-y)(x+y)-5(x+y)`
`=(x+y)(x-y-5)`
`m) 3x^2-6xy+3y^2-12z^2`
`=3(x^2-2xy+y^2-4z^2)`
`=3[(x-y)^2-(2z)^2]`
`=3(x-y-2z)(x-y+2z)`
`n) x^2+4x-y^2+4`
`=(x^2+4x+4)-y^2`
`=(x+2)^2-y^2`
`=(x-y+2)(x+y+2)`
bài 5:
`a) (x+1)(x+2)=x^2+2x+x+2=x^2+3x+2`
`b) (5x-1)/(3x^2y)+(x+1)/(3x^2y)`
`=(5x-1+x+1)/(3x^2y)`
`=(6x)/(3x^2y)`
`=2/(xy)`