m.n giúp mình với nhiều quá , em bt làm bài này ạ , chỉ cần đáp án thôi

3,

`4+8a+4a^2`

`=4(1+2a+a^2)`

`=4(1+a)^2`

4,

`25+a^2+10a`

`=a^2+2.a.5+5^2`

`=(a+5)^2`

5,

`x^2-2xy+y^2`

`=(x-y)^2`

6,

`4-4y+y^2`

`=2^2-2.2.y+y^2`

`=(2-y)^2`

7,

`25+4x^2-20x`

`=(2x)^2-2.2x.5+5^2`

`=(2x-5)^2`

8,

`9x^2-6x+1`

`=(3x)^2-2.3x.1+1^2`

`=(3x-1)^2`

9,

`25a^2+4b^2-20ab`

`=(5a)^2-2.5a.2b+(2b)^2`

`=(5a-2b)^2`

10,

`4a^2-12ab+9b^2`

`=(2a)^2-2.2a.3b+(3b)^2`

`=(2a-3b)^2`

11,

`4x^2+9+12x`

`=(2x)^2+2.2x.3+3^2`

`=(2x+3)^2`

12,

`16a^2+9-24a`

`=(4a)^2-2.4a.3+3^2`

`=(4a-3)^2`

13,

`25+4x^2-20x`

`=(2x)^2-2.2x.5+5^2`

`=(2x-5)^2`

14,

`x^2+6xy+9y^2`

`=x^2+2.x.3y+(3y)^2`

`=(x+3y)^2`

$\\$

$\\$

1,

`x^2-y^2=(x-y)(x+y)`

2,

`x^2-9=x^2-3^2=(x-3)(x+3)`

3,

`4x^2-1=(2x)^2-1^2=(2x-1)(2x+1)`

4,

`16-x^4`

`=4^2-(x^2)^2`

`=(4-x^2)(4+x^2)`

`=(2^2-x^2)(4+x^2)`

`=(2-x)(2+x)(4+x^2)`

5,

`4y^2-4x^2=4(y^2-x^2)=4(y-x)(y+x)`

6,

`16a^2-9y^2=(4a)^2-(3y)^2=(4a-3y)(4a+3y)`

7,

`81-4y^2=9^2-(2y)^2=(9-2y)(9+2y)`

8,

`-9+4x^2=4x^2-9=(2x)^2-3^2=(2x-3)(2x+3)`

9,

`1-25a^4=1^2-(5a^2)^2=(1-5a^2)(1+5a^2)`