thực hiện phép tính : (x3 - 2xx + 3x - 6) : (x - 2)
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\(\dfrac{x^3-2x^2+3x-6}{x-2}=\dfrac{x^2\left(x-2\right)+3\left(x-2\right)}{x-2}\\ =\dfrac{\left(x^2+3\right)\left(x-2\right)}{x-2}=x^2+3\)
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\(\left(x^3-2x^x+3x-6\right):\left(x-2\right)\)
\(=x^3:\left(x-2\right)-2x^x:\left(x-2\right)+3x:\left(x-2\right)-6:\left(x-2\right)\)
\(=x^3:x-x^3:2-2x^x:x+2x^x:2+3x:x-3x:2-6:x+6:2\)
\(=x^2-\dfrac{x^3}{2}-2x^{x-1}+x^x+3-\dfrac{3x}{2}-\dfrac{6}{x}+3\)
\(=x^2-\dfrac{x^3+3x}{2}-2x^{x-1}+x^x+6-\dfrac{6}{x}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1) \(\left(x^3-8\right):\left(x-2\right)=\left[\left(x-2\right)\left(x^2+2x+4\right)\right]:\left(x-2\right)=x^2+2x+4\)
2) \(\left(x^3-1\right):\left(x^2+x+1\right)=\left[\left(x-1\right)\left(x^2+x+1\right)\right]:\left(x^2+x+1\right)=x-1\)
3) \(\left(x^3+3x^2+3x+1\right):\left(x^2+2x+1\right)=\left(x+1\right)^3:\left(x+1\right)^2=x+1\)
4) \(\left(25x^2-4y^2\right):\left(5x-2y\right)=\left[\left(5x-2y\right)\left(5x+2y\right)\right]:\left(5x-2y\right)=5x+2y\)
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a) Ta có: ( x2 -1 )( x2 + 2x )
= x2( x2 + 2x ) - ( x2 + 2x )
= x4 + 2x3 - x2 - 2x
b) Ta có ( x + 3 )( x2 + 3x -5 )
= x( x2 + 3x -5 ) + 3( x2 + 3x -5 )
= x3 + 3x2 - 5x + 3x2 + 9x - 15
= x3 + 6x2 + 4x - 15
c) Ta có ( x -2y )( x2y2 - xy + 2y )
= x( x2y2 - xy + 2y ) - 2y( x2y2 - xy + 2y )
= x3y2 - x2y + 2xy - 2x2y3 + 2xy2 - 4y2
d) Ta có ( 1/2xy -1 )( x3 -2x -6 )
= 1/2xy( x3 -2x -6 ) - ( x3 -2x -6 )
= 1/2x4y - x2y - 3xy - x3 + 2x + 6
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\(a,\left(x^3+5x^2-2x+1\right)\left(x-7\right)\\ =x^4-7x^3+5x^3-35x^2-2x^2+14x+x-7\\ =x^4-2x^3-37x^2+15x-7\\ b,\left(2x^2-3xy+y^2\right)\left(x+y\right)\\ =2x^3+2x^2y-3x^2y-3xy^2+xy^2+y^3\\ =2x^3-x^2y-2xy^2+y^3\\ c,\left(x-2\right)\left(x^2-5x+1\right)-x\left(x^2+11\right)\\ =x^3-5x^2+x-2x^2+10x--x^3-11x\\ =x^3-7x^2\\ d,x\left(1-3x\right)\left(4-3x\right)-\left(x-4\right)\left(3x+5\right)\\ =x\left(4-15x+9x^2\right)-\left(3x^2-7x-20\right)\\ =4x-15x^2+9x^3-3x^2+7x+20\\ =9x^3-18x^2+11x+20\)
\(=\dfrac{x^2\left(x-2\right)+3\left(x-2\right)}{x-2}=x^2+3\)