giúp e vs ạk
`a)x^2-4y^2-4y-1`
`=x^2-(4y^2+4y+1)`
`=x^2-(2y+1)^2`
`=(x-2y-1)(x+2y+1)`
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`b)x^3-4x^2+12x-27`
`=x^3-3x^2-x^2+3x+9x-27`
`=x^2(x-3)-x(x-3)+9(x-3)`
`=(x-3)(x^2-x+9)`
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`c)2x^2+5x-7`
`=2x^2+7x-2x-7`
`=x(2x+7)-(2x+7)`
`=(2x+7)(x-1)`
a: \(=x^2-\left(2y+1\right)^2=\left(x-2y-1\right)\left(x+2y+1\right)\)
b: \(=\left(x-3\right)\left(x^2+3x+9\right)-4x\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-x+9\right)\)
c: \(=2x^2+7x-2x-7=\left(2x+7\right)\left(x-1\right)\)
a, \(x^2-4y^2-4y-1\)
\(=x^2-\left(4y^2+4y+1\right)\)
\(=x^2-\left[\left(2y\right)^2+2.2y.1+1^2\right]\)
\(=x^2-\left(2y+1\right)^2\)
\(=\left(x-2y-1\right)\left(x+2y+1\right)\)
b, \(x^3-4x^2+12x-27\)
\(=\left(x^3-3x^2\right)-\left(x^2-3x\right)+\left(9x-27\right)\)
\(=x^2\left(x-3\right)-x\left(x-3\right)+9\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-x+9\right)\)
c, \(2x^2+5x-7\)
\(=\left(2x^2-2x\right)+\left(7x-7\right)\)
\(=2x\left(x-1\right)+7\left(x-1\right)\)
\(=\left(x-1\right)\left(2x+7\right)\)
