$\text{ Bài 1:}$
`e)`
`(x^2)/(4)+2xy+4y^2`
`=(x/2)^2+2. x/2 .2y+(2y)^2`
`=(x/2 +2y)^2`
`f)`
`-x^2+10x-25`
`=-(x^2-10x+25)`
`=-(x^2-2.x.5+5^2)`
`=-(x-5)^2`
`f)`
`9(2x+3)^2-4(x+1)^2`
`=[3(2x+3)]^2-[2(x+1)]^2`
`=(6x+9)^2-(2x+2)^2`
`=[(6x+9)+(2x+2)].[(6x+9)-(2x+2)]`
`=(6x+9+2x+2).(6x+9-2x-2)`
`=(8x+11).(4x+7)`
`m)`
`2bc-(b^2+c^2-a^2)`
`=2bc-b^2-c^2+a^2`
`=a^2-(b^2-2bc+c^2)`
`=a^2-(b-c)^2`
`=[a+(b-c)].[a-(b-c)]`
`=(a+b-c).(a-b+c)`
$\text{ Bài 2:}$
`d)`
`x^3+3/2 x^2+3/4 x+1/8`
`=x^3 + 3.x^2 . 1/2 + 3 . (1/2)^2 .x+(1/2)^3`
`=(x+1/2)^3`
AD: `a^3+3a^2 b+3ab^2+b^3=(a+b)^3`
`e)`
`27x^3-54x^2 y+36xy^2 -8y^3`
`=(3x)^3-3.(3x)^2 .2y+3.3x.(2y)^2-(2y)^3`
`=(3x-2y)^3`
AD: `a^3-3a^2 b+3ab^2-b^3=(a-b)^3`
