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1: \(x-9=\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)\)
2: \(x-16=\left(\sqrt{x}-4\right)\left(\sqrt{x}+4\right)\)
3: \(9x-1=\left(3\sqrt{x}-1\right)\left(3\sqrt{x}+1\right)\)
4: \(x\sqrt{x}+1=\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)\)
\(1,x-9=\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)\\ 2,x-16=\left(\sqrt{x}-4\right)\left(\sqrt{x}+4\right)\\ 3,9x-1=\left(3\sqrt{x}-1\right)\left(3\sqrt{x}+1\right)\\ 4,x\sqrt{x}+1=\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Lần sau bạn cần chú ý viết đầy đủ yêu cầu đề bài.
Coi đây là bài toán rút gọn/ khai triển.
Ta có:
$(1+2x)(1-2x)-x(x+2)(x-2)$
$=1^2-(2x)^2-x(x^2-2^2)$
$=1-4x^2-x(x^2-4)=-x^3-4x^2+4x+1$
\(=1-4x^2-x\left(x^2-4\right)\)
\(=1-4x^2-x^3+4x\)
\(=-x^3+x^2-5x^2+5x-x+1\)
\(=-x^2\left(x-1\right)-5x\left(x-1\right)-\left(x-1\right)\)
\(=\left(x-1\right)\left(-x^2-5x-1\right)\)
\(=\left(1-x\right)\left(x^2+\dfrac{2x.5}{2}+\dfrac{25}{4}-\dfrac{21}{4}\right)\)
\(=\left(1-x\right)\left(\left(x+\dfrac{5}{2}\right)^2-\dfrac{21}{4}\right)\)
\(=\left(1-x\right)\left(x+\dfrac{5}{2}-\dfrac{\sqrt{21}}{2}\right)\left(x+\dfrac{5}{2}+\dfrac{\sqrt{21}}{2}\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x^3+9x^2+27x+27=\left(x+3\right)^3\)
b) \(3\sqrt{3x^3}+18x^2+12\sqrt{3x}+8=\left(\sqrt{3x}+2\right)^3\)
c) \(\dfrac{1}{4}-x^2=\left(\dfrac{1}{2}-x\right)\left(\dfrac{1}{2}+x\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(4x^2-4x+1\right)-\left(x-1\right)^2\)
\(=\left(2x-1\right)^2-\left(x-1\right)^2\)
\(=\left(2x-1-x+1\right)\left(2x-1+x-1\right)\)
\(=x\left(3x-2\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a, \(\dfrac{x^2}{4}-xy+y^2=\left(\dfrac{x}{2}\right)^2-xy+y^2=\left(\dfrac{x}{2}\right)^2-2.\dfrac{x}{2}.y+y^2\)
\(=\left(\dfrac{x^2}{2}-y\right)^2\)
b, \(x^2+x+\dfrac{1}{4}=x^2+\dfrac{1}{2}.2.x+\left(\dfrac{1}{2}\right)^2=\left(x+\dfrac{1}{2}\right)^2\)
c, \(x^2+2\sqrt{3}x+3=x^2+2\sqrt{3}x+\left(\sqrt{3}\right)^2=\left(x+\sqrt{3}\right)^2\)
d, \(4x^2-1=\left(2x-1\right)\left(2x+1\right)\)
`x^2/4-2*x/2*y+y^2`
`=(x/2-y)^2`
`x^2+x+1/4`
`=x^2+2*x*1/2+(1/2)^2`
`=(x+1/2)^2`
`x^2+2sqrt3x+3`
`=x+2xsqrt3+sqrt3^2`
`=(x+sqrt3)^2`
`4x^2-1`
`=(2x)^2-1`
`=(2x-1)(2x+1)`
![](https://rs.olm.vn/images/avt/0.png?1311)
\(=x\sqrt{x}-1=\left(\sqrt{x}\right)^3-1^3=\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)\)