Đáp án + Giải thích các bước giải:
`1)A=9-(x-y)^2=3^3-(x-y)^2=(3+x-y)(3-x+y)`
`2)A=x^2+6x+9-y^2=x^2+2.3.x+3^3-y^2=(x+3)^2-y^2=(x+3+y)(x+3-y)`
`3)A=(x-y)^2-4=(x-y)^2-2^2=(x-y+2)(x-y-2)`
`4)A=x^2+4x-y^2+4=(x^2+4x+4)-y^2=(x^2+2.2.x+2^2)-y^2=(x+2)^2-y^2=(x+2+y)(x+2-y)`
`5)A=(x+y)^2-9x^2=(x+y)^2-(3x)^2=(x+y+3x)(x+y-3x)=(4x+y)(-2x+y)`
`6)A=9-x^2-2xy-y^2=9-(x^2+2xy+y^2)=3^2-(x-y)^2=(3+x-y)(3-x+y)`
Chúc bạn học tốt!
