Đáp án + Giải thích các bước giải:
`a)` `(3-xy^2)^2-(2+xy^2)^2`
`=[(3-xy^2)-(2+xy^2)][(3-xy^2)+(2+xy^2)]`
`=(3-xy^2-2-xy^2)(3-xy^2+2+xy^2)`
`=(1-2xy^2)*5=5-10xy^2`
`b)` `9x^2-(3x-4)^2`
`=(3x)^2-(3x-4)^2`
`=(3x-3x+4)(3x+3x-4)`
`=4(6x-4)=24x-16`
`c)` `(a-b^2)(a+b^2)=a^2-(b^2)^2=a^2-b^4`
`d)` `(a^2+2a+3)(a^2+2a-3)=(a^2+2a)^2-3^2`
`=(a^2)^2+2*a^2*2a+(2a)^2-9`
`=a^4+4a^3+4a^2-9`
`e)` `(x-y+6)(x+y-6)=[x-(y-6)][x+(y-6)]`
`=x^2-(y-6)^2`
`=x^2-(y^2-12y+36)`
`=x^2-y^2+12y-36`
`f)` `(y+2z-3)(y-2z-3)=[y+(2z-3)][y-(2z+3)]`
`=y^2-(2z-3)^2`
`=y^2-(4z^2-12z+9)`
`=y^2-4z^2+12z-9`.