Đáp án + Giải thích các bước giải:
`1.`
`a)` `4x^2+4x+1`
`=(2x)^2+2*2x*1+1^2`
`=(2x+1)^2`
`b)` `9x^2-12x+4`
`=(3x)^2-2*3x*2+2^2`
`=(3x-2)^2`
`c)` `x^2/4+x/2+1/4=(x/2)^2 + 2*x/2*1/2 + (1/2)^2 = [(x+1)/2]^2`
`d)` `9/(4x^2)+(9y^2)/4-(9y)/(2x) = (9/4x^2)+9/4y^2-(9y)/(2x)=(3/2x)^2-2*3/2x*3/2y+(3/2y)^2`
`=(3/2x-3/2y)^2`
`e)` `25x^2-9/4=(5x)^2-(3/2)^2=(5x-3/2)(5x+3/2)`
`f)` `4x^2-1/9(y+1)^2=(2x)^2-(y+1)^2/9`
`=(2x)^2-((y+1)/3)^2=(2x-(y+1)/3)(2x+(y+1)/3)`
