1: \(=6x^2+2x-15x-5-x^2+6x-9+4x^2+20x+25-27x^3-27x^2-9x-1\)

=-27x^3-18x^2+4x+10

2: =4x^2-1-6x^2-9x+4x+6-x^3+3x^2-3x+1+8x^3+36x^2+54x+27

=7x^3+37x^2+46x+33

5:

\(=25x^2-1-x^3-27-4x^2-16x-16-9x^2+24x-16+\left(2x-5\right)^3\)

\(=8x^3-60x^2+150-125+12x^2-x^3+8x-60\)

=7x^3-48x^2+8x-35

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

\(=9x^2-12x+4-4x^2+9\)

\(=5x^2-12x+13\)

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

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

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

\(=11x^2-7x+2x^3+2\)

a: Đặt A=3(5x-2)-|x-5|

TH1: x>=5

=>x-5>=0

A=3(5x-2)-|x-5|

=15x-6-(x-5)

=15x-6-x+5

=14x-1

TH2: x<5

=>x-5<0

A=3(5x-2)-|x-5|

=15x-6-(5-x)

=15x-6-5+x

=16x-11

b: Đặt B=|2x+3|+2x+7

TH1: x>=-3/2

=>2x+3>=0

B=|2x+3|+2x+7

=2x+3+2x+7

=4x+10

TH2: x<-3/2

=>2x+3<0

B=|2x+3|+2x+7

=-2x-3+2x+7

=4

c: đặt C=3x-1+|1-3x|

=3x-1+|3x-1|

TH1: x>=1/3

=>3x-1>=0

C=3x-1+|3x-1|

=3x-1+3x-1

=6x-2

TH2: x<1/3

=>3x-1<0

C=3x-1+|3x-1|

=3x-1+1-3x

=0

d: Đặt D=3(x-1)-2|x+3|

TH1: x>=-3

=>x+3>=0

D=3(x-1)-2|x+3|

=3(x-1)-2(x+3)

=3x-3-2x-6

=x-9

TH2: x<-3

=>x+3<0

D=3(x-1)-2|x+3|

=3x-3-2(-x-3)

=3x-3+2x+6

=5x+3

1) 30x-30x^2-31

2)6x^4-2x^3-15x^2+23x-6

$\textbf{1)}$

$(3x-5)(7-5x)-(5x+2)(2-3x)$

$=(21x-15x^2-35+25x)-(10x-15x^2+4-6x)$

$=-15x^2+46x-35+15x^2-4x-4$

$=42x-39$

$=3(14x-13).$

a)      \(2x\left(5-3x^2\right)-10\left(6+x\right)\)

     \(=10x-6x^3-60-10x\)

     \(=\) \(-6x^3-60\)

a) \(2x\left(5-3x^2\right)-10\left(6+x\right)\\ =2x.5-2x.3x^2-10.6-10.x\\ =10x-6x^3-60-10x\)

b) \(3\left(-x+2\right)-6\left(1-x+5x^{20}\right)\\ =-3.x+3.2-6.1+6.x-5.5x^{20}\\ =-3x+6-6+6x-25x^{20}=25x^{20}+3x\)

c) \(7x\left(2-5x^2+\dfrac{1}{2}x^3\right)-14x\left(1-2x^2\right)\\ =7x.2-7x.5x^2+7x.\dfrac{1}{2}x^3-14x.1+14x.2x^2\\ =14x-25x^3+\dfrac{7}{2}x^4-14x+28x^3=3x^2+\dfrac{7}{2}x^4\) 

a: Ta có: \(\left(8x^3-4x^2\right):4x-\left(4x^2-5x\right):2x+\left(2x\right)^2\)

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

\(=6x^2-3x+\dfrac{5}{2}\)

b: Ta có: \(\left(3x^3-x^2y\right):x^2-\left(xy^2+x^2y\right):xy+2x\left(x-1\right)\)

\(=3x-y-y-x+2x^2-2x\)

\(=2x^2-2y\)

\(a,3x\left(x-2\right)-5x\left(1-x\right)-8\left(x^2-3\right)\)

\(=3x^2-6x-5x+5x^2-8x^2+24\)

\(=\left(3x^2+5x^2-8x^2\right)+\left(-6x-5x\right)+24\)

\(=0-11x+24\)

\(=-11x+24\)

\(b,\left(7x-3\right)\left(2x+1\right)-\left(5x-2\right)\left(x+4\right)-9x^2+17x\)

\(=14x^2+7x-6x-3-5x^2-20x+2x+8-9x^2+17x\)

\(=\left(14x^2-5x^2-9x^2\right)+\left(7x-6x-20x+2x+17x\right)+\left(-3+8\right)\)

\(=0+0+5\)

\(=5\)