a) Thực hiện phép tính:
3x(4x - 3) - (2x - 1) (6x + 5 )
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26:
A=12x^2+10x-6x-5-(12x^2-8x+3x-2)
=12x^2+4x-5-12x^2+5x+2
=9x-3
Khi x=-2 thì A=-18-3=-21
25:
b: \(\left(y-3\right)\left(y^2+y+1\right)-y\left(y^2-2\right)\)
=y^3+y^2+y-3y^2-3y-3-y^3+2y
=-2y^2-3
\(a,=12x^2-4x-6x-2-x-3=12x^2-11x-5\\ b,=12x^2-9x-12x^2-4x+5=5-13x\\ c,=12x^3-4x^2-12x^3-12x^2+7x-3=-16x^2+7x-3\\ d,=\left(x^2-4\right)\left(x^2+4\right)=x^4-16\)
a: \(=2x^3:\dfrac{-3}{2}x+4x:\dfrac{3}{2}x-5:\dfrac{3}{2}\)
=-4/3x^2+8/3-10/3
=-4/3x^2-2/3
d: \(\dfrac{3x^3-5x+2}{x-3}=\dfrac{3x^3-9x^2+9x^2-27x+22x-66+68}{x-3}\)
\(=3x^2+9x+22+\dfrac{68}{x-3}\)
a) 3x.(x² - 2)
= 3x.x² + 3x.(-2)
= 3x³ - 6x
b) (6x³ + 2x² - 4x) : 2x
= 6x³ : 2x + 2x² : 2x - 4x : 2x
= 3x² + x - 2
c) 2x(x² - 1)
= 2x.x² - 2x.1
= 2x³ - 2x
=3x(x^2-2)(3x^2+x-2)
=(3x^3-6x)(3x^2+x-2)
=9x^5+3x^4-6x^3-18x^3-6x^2+12x
=9x^5+3x^4-12x^3-6x^2+12x
2x(x^2-1)=2x^3-2x
a: =x^4-3x^5+4x^8
b: =2x^3+2x^2+4x
c: =4x^2+8x-5
d: =2x+3x^2+7x^4
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) \(\left(4x^3-4x^2-5x+4\right):\left(2x+1\right)\)
\(=2x^2+4x^3-2x-4x^2-\dfrac{5}{2}-5x+\dfrac{2}{x}+4\)
\(=4x^3-2x^2-7x+\dfrac{2}{x}+\dfrac{3}{2}\)
\(\frac{4x+1}{3x}+\frac{2x-3}{6x}\)
\(=\frac{2\left(4x+1\right)}{6x}+\frac{2x-3}{6x}\)
\(=\frac{2\left(4x+1\right)+\left(2x-3\right)}{6x}\)
\(=\frac{8x+2+2x-3}{6x}\)
\(=\frac{10x-1}{6x}\)
\(3x\left(4x-3\right)-\left(2x-1\right)\left(6x+5\right)\\ =12x^2-9x-\left(12x^2+10x-6x-5\right)\)
\(=12x^2-9x-\left(12x^2+4x-5\right)\\ =5-13x\)