Đáp án:
Bài `1`:
`a. x^2-25=x^2-5^2=(x-5)(x+5)`
`b. x^3-8=x^3-2^3=(x-2)(x^2+2x+4)`
`c. (2x-5)^2-16=(2x-5)^2-4^2=(2x-5+4)(2x-5-4)=(2x-1)(2x-9)`
`d. 9x^2-12xy+4y^2=(3x)^2-2.3x.2y+(2y)^2=(3x-2y)^2`
`e. x^3-6x^2+12x-8=x^3-3.x^2 .2+3.x.2^2-2^3=(x-2)^3`
Bài `2`:
`a. x^3+x^2+x+1=x^2(x+1)+(x+1)=(x+1)(x^2+1)`
`b. x^2y+xy^2-x-y=xy(x+y)-(x+y)=(x+y)(xy-1)`
`c. x^2-xy+5x-5y=x(x-y)+5(x-y)=(x-y)(x+5)`
`d. 2x^2-x-6xy+3y=x(2x-1)-3y(2x-1)=(2x-1)(x-3y)`