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\(27x^3-1\) =\(\left(3x\right)^3-1^3\)
Nhớ tick và theo dõi mình nha!
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Bài 1:
\(B=\dfrac{1}{9}x^2-2x+9\)
\(=\left(\dfrac{1}{3}x\right)^2-2\cdot\dfrac{1}{3}x\cdot3+3^2=\left(\dfrac{1}{2}x-3\right)^2\)
\(C=x^3-9x^2+27x-27=\left(x-3\right)^3\)
\(D=27x^3+27x^2+9x+1=\left(3x+1\right)^3\)
\(E=\left(x-2y\right)^3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(27x^3-54x^2y+36xy^2-8y^3\)
\(=\left(3x-2y\right)^3\)
Tại \(x=4;\)\(y=6\) thì gtbt là:
\(\left(3.4-2.6\right)^3=0\)
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27x3 - 8y3
= ( 3x )3 - ( 2y )3
= ( 3x - 2y ) ( 9x2 + 6xy + 4y2 )
.....
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\(8-27x^3\)
\(=2^3-\left(3x\right)^3\)
\(=\left(2-3x\right)\left(4+6x+9x^2\right)\)
a) \(8-27x^3=\left(2-x\right)\left(4+6x+9x^2\right)\)
b) \(27+27x+9x^2+x^3=\left(3+x\right)^3\)
c) \(x^3+8y^3=\left(x+2y\right)\left(x^2-2xy+4y^2\right)\)
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\(27x^3-8y^3=\left(3x\right)^3-\left(2y\right)^3=\left(3x-2y\right)\left(9x^2+6xy+4y^2\right)\)
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\(D=27x^3-\dfrac{1}{8}y^3\)
\(D=\left(3x\right)^3-\left(\dfrac{1}{2}y\right)^3\)
\(D=\left(3x-\dfrac{1}{2}y\right)\left(9x^2+3x.\dfrac{1}{2}y+\dfrac{1}{4}y^2\right)\)
\(C=\left(x^2+2x+3\right)^2-9\)
\(C=\left(x^2+2x+3\right)^2-3^2\)
\(C=\left(x^2+2x+3+3\right)\left(x^2+2x+3-3\right)\)
\(C=\left(x^2+2x+6\right)\left(x^2+2x\right)\)
\(27x^3-8y^3\)
\(=\left(3x\right)^3-\left(2y\right)^3\)
\(=\left(3x-2y\right)\left(9x^2+6xy+4y^2\right)\)