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\(3x^2-6x+9x^2=12x^2-6x=6x\left(2x-1\right)\)
\(-9x^2+6x+y^2-1\)
\(=-\left(9x^2-6x+1-y^2\right)\)
\(=-\left(3x-1-y\right)\left(3x-1+y\right)\)
1. \(x^3+2x^2-6x-27=\left(x-3\right)\left(x^2+5x+9\right)\)
2. \(9x^2+6x-4y^2-4y=\left(9x^2-4y^2\right)+\left(6x-4y\right)\)
\(=\left(3x-2y\right)\left(3x+2y\right)+2\left(3x-2y\right)=\left(3x-2y\right)\left(3x+2y+2\right)\)
3. \(12x^3+4x^2-27x-9=4x^2\left(3x+1\right)-9\left(3x+1\right)\)
\(=\left(3x+1\right)\left(x^2-\dfrac{9}{4}\right)=\left(x+\dfrac{1}{3}\right)\left(x+\dfrac{3}{2}\right)\left(x-\dfrac{3}{2}\right)\)
1) Ta có: \(x^3+2x^2-6x-27\)
\(=\left(x-3\right)\left(x^2+3x+9\right)+2x\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2+5x+9\right)\)
2: Ta có: \(9x^2+6x-4y^2-4y\)
\(=\left(3x-2y\right)\left(3x+2y\right)+2\left(3x-2y\right)\)
\(=\left(3x-2y\right)\left(3x+2y+2\right)\)
\(x^3+9x^2+6x-16\)
\(=x^3+x^2-2x+8x^2+8x-16\)
\(=x\left(x^2+x-2\right)+8\left(x^2+x-2\right)\)
\(=\left(x^2+x-2\right)\left(x+8\right)\)
\(=\left(x^2-x+2x-2\right)\left(x+8\right)\)
\(=\left[x\left(x-1\right)+2\left(x-1\right)\right]\left(x+8\right)\)
\(=\left(x-1\right)\left(x+2\right)\left(x+8\right)\)
\(x^3+6x^2+9x=x\left(x^2+6x+9\right)=x\left(x+3\right)^2\)
\(x^3+6x^2+9x\)
\(=x\left(x^2+6x+9\right)\)
\(=x\left(x+3\right)^2\)
a) \(27x^3+27x^2+9x+1=\left(3x+1\right)^3\)
b) \(-x^3-3x^2-3x-1=-\left(x^3+3x^2+3x+1\right)=-\left(x+1\right)^3\)
c) \(-8+12x-6x^2+x^3=\left(x-2\right)^3\)
\(=9x^3-3x^2-9x^2+6x-1\)1
\(=3x^2\left(3x-1\right)-\left(9x^2-6x+1\right)\)
\(=3x^2\left(3x-1\right)-\left(3x-1\right)^2\)
\(=\left(3x-1\right)\left(3x^2-3x+1\right)\)
\(9x^2-6x^2-3\)
\(=3x^2-3\)
\(=3.\left(x^2-1\right)\)
\(=3.\left(x-1\right).\left(x+1\right)\)
\(9x^2-6x^2-3\)
\(=3x^2-3\)
\(=3.\left(x^2-1\right)\)
\(=3.\left(x-1\right).\left(x+1\right)\)
Nguồn: kudo shinichi