Đáp án:
`a)x^3-16x=x(x^2-16)=x(x−4)(x+4)`
`b)3x^2+3y^2-6xy-12`
=3(x^2-2xy+y^2-4)
`=3[ ( x- y)^2-2^2 )]`
`=3(x-y-2)(x-y+2)`
`c)x^2+6x+5=x^2+5x+x+5=x(x+5)+(x+5)=(x+1)(x+5)`
`d)x^4+x^3+2x^2+x+1=x^4+x^3+x^2+x^2+x+1=x^2(x^2+x+1)+(x^2+x+1)=(x^2+x+1)(x^2+1)`