Đáp án+Giải thích các bước giải:
`1)x^2-6x+9=(x-3)^2`
`2)25+10x+x^2=5^2+2.5x+x^2`
`=(5+x)^2`
`3)1/4a^2+2ab^2+4b^4``=(1/2a)^2+2. 1/2 .2.ab^2+(2b^2)^2`
`=(1/2a+2b^2)^2`
`4)``1/9-2/3y^4+y^8``=(1/3)^2-2. 1/3.y^4+(y^4)^2`
`=(1/3-y^4)^2`
`5)``x^2-10x+25=``x^2-2.5x+5^2`
`=(x-5)^2`
`6)``x^2+4xy+4y^2=``x^2+2.2xy+(2y)^2`
`=(x+2y)^2`
`7)(3x+2)^2-4=``(3x+2)^2-2^2`
`=(3x+2+2)(3x+2-2)`
`=3x(3x+4)`
`8)4x^2-25y^2=(2x)^2-(5y)^2`
`=(2x+5y)(2x-5y)`
`9)4x^2-49=(2x)^2-7^2`
`=(2x+7)(2x-7)`
`10)4x^2+4x+1=(2x)^2+2.2x+1^2`
`=(2x+1)^2`
`11)x^2-20x+100=x^2-2.10x+10^2`
`=(x-10)^2`
`12)y^4-14y^2+49=(y^2)^2-2.7.y^2+7^2`
`=(y^2-7)^2`