`a)3x(2x^2-3x+4)`

`=6x^3-9x^2+12x`

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`b)(x+3)^2+(3x-2)(x+4)`

`=x^2+6x+9+3x^2+12x-2x-8`

`=4x^2+16x+1`

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`c)[2x-4]/[x-1]+[2x+2]/[x^2-1]`       `ĐK: x \ne +-1`

`=[(2x-4)(x+1)+2x+2]/[(x-1)(x+1)]`

`=[2x^2+2x-4x-4+2x+2]/[(x-1)(x+1)]`

`=[2x^2-2]/[x^2-1]`

`=2`

hếp

a: =2x^5-15x^3-x^2-2x^5-x^3=-16x^3-x^2

b: =x^3+3x^2-2x-3x^2-9x+6

=x^3-11x+6

c: \(=\dfrac{4x^3+2x^2-6x^2-3x-2x-1+5}{2x+1}\)

\(=2x^2-3x-1+\dfrac{5}{2x+1}\)

a) \(6x^3\left(\dfrac{1}{3}x^2-\dfrac{5}{2}-\dfrac{1}{6}\right)-2x^5-x^3\)

\(=6x^3\left(\dfrac{1}{3}x^2-\dfrac{16}{6}\right)-2x^5-x^3\)

\(=2x^5-16x^3-2x^5-x^3\)

\(=-17x^3\)

b) \(\left(x+3\right)\left(x^2+3x-2\right)\)

\(=x^3+3x^2-2x+3x^2+9x-6\)

\(=x^3+6x^2+7x-6\)

c) \(\left(4x^3-4x^2-5x+4\right):\left(2x+1\right)\)

\(=2x^2+4x^3-2x-4x^2-\dfrac{5}{2}-5x+\dfrac{2}{x}+4\)

\(=4x^3-2x^2-7x+\dfrac{2}{x}+\dfrac{3}{2}\)

a: \(3x^2y\left(2x^2-xy+5y^2\right)=6x^4y-3x^3y^2+15x^2y^3\)

b: \(\left(x+2\right)\left(x^2+3x-4\right)\)

\(=x^3+3x^2-4x+2x^2+6x-8\)

\(=x^3+5x^2+2x-8\)

a)\(\left(2x^2-3x\right)\left(5x^2-2x+1\right)\)

\(=2x^2\left(5x^2-2x+1\right)-3x\left(5x^2-2x+1\right)\)

\(=10x^4-4x^3+2x^2-15x^3+6x^2-3x\)

\(=10x^4-19x^3+8x^2-3x\)

a. \(\left(2x^2-3x\right)\left(5x^2-2x+1\right)\)

\(=10x^4-4x^3+2x^2-15x^3+6x^2-3x\)

\(=10x^4-19x^3+8x^2-3x\)

b. \(\left(2x^4-x^3+3x^2\right):\left(\frac{1}{3}x^2\right)\)

\(=\left(2x^4-x^3+3x^2\right).\frac{3}{x^2}\)

\(=0,6x^2-3x+0,9\)

a) \(18x^4y^3:12\left(-x\right)^3y\)

\(=\left(18:-12\right)\left(x^4:x^3\right)\left(y^3:y\right)\)

\(=-\dfrac{3}{2}xy^2\)

b) \(x^2y^2-2xy^3:\dfrac{1}{2}xy^2\)

\(=\dfrac{xy^2\left(x-2y\right)}{\dfrac{1}{2}xy^2}\)

\(=\dfrac{x-2y}{\dfrac{1}{2}}\)

\(=2x-4y\)

1: \(4xy\left(x^2-2xy+3y^2\right)=4x^3y-8x^2y^2+12xy^3\)

2: \(\left(x^2-2\right)\left(x^4+2x^2+4\right)=x^6-8\)

b: \(=2x^2-3x+10x-15=2x^2+7x-15\)

$=(6x^2+x-2)(3-x)$

$=18x^2-6x^3+3x-x^2-6+2x$

$=-6x^3+17x^2+5x-6$