Question

Rút gọn biểu thức

 

A = x² ( x - 2 ) + x ( 1 - x ) + x ( 2x + 3 ) - 5x ( x + 1 )

B = x² ( 11x - 2 ) + x² ( x - 1 ) - 3x ( 4x² - x - 2 ) 

C = ( 5x - 1 ) ( x + 3 ) - ( x - 2 ) ( 5x - 4 )

Answer 1

\(A=x^3-2x^2+x-x^2+2x^2+3x-5x^2-5x\\ A=\left(-2x^2-x^2+2x^2-5x^2\right)+\left(x+3x-5x\right)+x^3\\ A=-6x^2-x+x^3\)

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\(B=11x^3-2x^2+x^3-x^2-12x^3+3x^2+6x\\ B=\left(11x^3+x^3-12x^3\right)+\left(-2x^2-x^2+3x^2\right)+6x\\ B=6x\)

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\(C=5x^2-x+15x-3-\left(5x^2-10x-4x+8\right)\\ C=5x^2-x+15x-3-5x^2+10x+4x-8\\ C=\left(5x^2-5x^2\right)+\left(-x+15x+10x+4x\right)+\left(-8-3\right)=28x-11\)