Toán Lớp 8: Tính :
a. ( 3x+1 ) ( 9x ^2-3x+1 ) +3x ^2( 3x-2 )
b. 4x( x-2 0 – ( 2x+3 )^2
c. ( 3x^3-5x^2+1 ) : ( x^2-x+1 )
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Toán Lớp 8: Tính :
a. ( 3x+1 ) ( 9x ^2-3x+1 ) +3x ^2( 3x-2 )
b. 4x( x-2 0 – ( 2x+3 )^2
c. ( 3x^3-5x^2+1 ) : ( x^2-x+1 )
help;-;
Comments ( 1 )
$a)$ $\left(3x+1\right)\left(9x^2-3x+1\right)+3x^2\left(3x-2\right)$
$=27x^3+1+3x^2\left(3x-2\right)$
$=27x^3+1+9x^3-6x^2$
$=27x^3+9x^3-6x^2+1$
$=36x^3-6x^2+1$
$b)$ $4x\left(x-20-\left(2x+3\right)^2\right)$
$=4x\left(x-20-4x^2-12x-9\right)$
$=4x\left(-4x^2-11x-29\right)$
$c)$ $\left(\:3x^3-5x^2+1\:\right)\::\:\left(\:x^2-x+1\:\right)$
$=3x+\dfrac{-2x^2-3x+1}{x^2-x+1}$
$=3x-2+\dfrac{-5x+3}{x^2-x+1}$