$bài$`1`
`a,4x^2-12x+9`
`=(2x)^2-2.2x.3+(3)^2`
`=(2x-3)^2`
`b,4x^2+4x+1`
`=(2x)^2+2.2x.1+1`
`=(2x+1)^2`
`c,1+12x+36x^2`
`=(6x)^2+2.6x+1`
`=(6x+1)^2`
$bài$ `2`
`d,(3x+1)^2-4(x-2)^2`
`=(3x+1)^2-[2(x-2)]^2`
`=(3x+1-2x+4)(3x+1+2x-4)`
`=(x+5)(5x-3)`
`e,9(2x+3)^2-4(x+1)^2`
`=[3(2x+3)]^2-[2(x+1)]^2`
`=(6x+9-2x-2)(6x+9+2x+2)`
`=(4x+7)(8x+11)`
`f,4b^2c^2-(b^2+c^2-a^2)^2`
`=(2bc)^2-(b^2+c^2-a^2)^2`
`=(2bc-b^2-c^2+a^2)(2bc+b^2+c^2-a^2)`
`=[a^2-(b^2-2bc+c^2)][(b^2+2bc+c^2)-a^2]`
`=[a^2-(b-c)^2][(b+c)^2-a^2]`
`=(a-b+c)(a+b-c)(b+c-a)(b+c+a)`
$bài$ `3`
`b,8x^6y^3+1`
`=(2x^2y)^3+1`
`=(2x^2y+1)(4x^4y^2-2x^2y+1)`
`text{CHÚC BN HỌC TỐT}`
