A = (x - 1)³ - x(x - 2)² + 1

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

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

A = x³ - 2x² + x - (x² - 2x + 1) - x(x² - 2x.2 + 2²) + 1

A = x³ - 2x² + x - (x² - 2x + 1) - (x³ - 4x² + 4x) + 1

A = x³ - 2x² + x - x² + 2x - 1 - x³ + 4x² - 4x + 1

A = (x³ - x³) + (-2x² - x² + 4x²) + (x + 2x - 4x) + (-1 + 1)

A = x² - x

B = (-x - 2)³ + (2x - 4)(x² + 2x + 4) - x²(x - 6)

B = (-x - 2)[(-x²) - 2.(-x).2 + 2²] + (2x - 4)(x² + 2x + 4) - x²(x - 6)

B = -x[(-x)² - 2.(-x).2 + 2²] - 2[(-x)² - 2.(-x).2 + 2²] + (2x - 4)(x² + 2x + 4) - x²(x - 6)

B = -(x³ + 4x² + 4x) - (2x² + 4x + 8) + 2x(x² + 2x + 4) - 4(x² + 2x + 4) - x²(x - 6)

B = -(x³ + 4x² - 4x) - (2x² + 4x + 8) + 2x³ + 4x² + 8x - (x² + 8x + 16) - (x³ - 6x²)

B = -x³ - 4x² + 4x - 2x² - 4x - 8 + 2x³ + 4x² + 8x - x² - 8x - 16 - x³ + 6x²

B = (-x³ + 2x³ - x³) + (-4x² - 2x² + 4x² - x² + 6x²) + (-4x - 8x + 8x - 8x) + (-8 - 16)

B = -12x - 24

a: =6x-3-|x-5|

Trường hợp 1: x>=5

A=6x-3-x+5=5x+2

Trường hợp 2: x<5

A=6x-3-(5-x)=6x-3+x-5=7x-8

b: Trường hợp 1: x>=-3/2

A=2x+3+x+2=3x+5

Trường hợp 2: x<-3/2

A=-2x-3+x+2=-x-1

`a)3(2x-1)-|x-5|`

`@TH1: x-5 >= 0<=>x >= 5=>|x-5|=x-5`

   `=>3(2x-1)-(x-5)=6x-3-x+5=5x+2`

`@TH2: x-5 < 0<=>x < 5=>|x-5|=5-x`

   `=>3(2x-1)-(5-x)=6x-3-5+x=7x-8`

____________________________________________________

`b)|2x+3|+x+2`

`@TH1:2x+3 >= 0<=>x >= [-3]/2=>|2x+3|=2x+3`

     `=>2x+3+x+2=3x+5`

`@TH2:2x+3 < 0<=>x < [-3]/2 =>|2x+3|=-2x-3`

     `=>-2x-3+x+2=-x-1`   

a.ta có

\(\left(x+3\right)^3+\left(x^2+1\right)\left(x-2\right)=x^3+9x^2+27x+27+x^3-2x^2+x-2\)

\(=2x^3+7x^2+28x+25\)

b.\(\left(2x-1\right)^2-\left(2-x\right)^3=4x^2-4x+1+x^3-6x^2+12x-8\)

\(=x^3-2x^2+8x-7\)

a) (x + 3)³ + (x² + 1)(x - 2)

= x³ + 9x² + 27x + 27 + x³ - 2x + x - 2

= x³ + x³ + 9x² + 27x - 2x + x + 27 - 2

= 2x³ + 9x² + 26x + 25

b) (2x - 1)² - (2 - x)³

= 4x² - 4x + 1 - ( 8 - 12x + 6x² - x³)

= 4x² - 4x + 1 - 8 + 12x - 6x² + x³  

= x³ + 4x² - 6x² + 12x - 4x + 1 -  8

= x³ - 2x² + 8x - 7

`Answer:`

`a)`

`A=5(x+1)^2-3(x-3)^2-4(x^2-4)`

`=>A=5(x^2+2x+1)-3(x^2-6x+9)-4x^2+16`

`=>A=5x^2+10x+5-3x^2+18x-27-4x^2+16`

`=>A=(5x^2-3x^2-4x^2)+(10x+18x)+(5-27+16)`

`=>A=-2x^2+28x-6`

`b)`

`B=5(x+1)^2-3(x-3)^2-4(x+2)(x-2)`

`=2x(3x+5)-3(3x+5)-2x(x^2-4x+4)-[(2x)^2-3^2]`

`=6x^2+10x-9x-15-2x^3+8x^2-8x-4x^2+9`

`=(6x^2-4x^2+8x^2)-2x^3+(10x-9x-8x)+(-15+9)`

Thay `x=-7` vào ta được:

`B=10(-7)^2-2(-7)^3-7(-7)-6`

`=>B=10.49-2(-343)+49-6`

`=>B=490+686+49-6`

`=>B=1219`

a: =18x^3y^2-12x^3y^3+6x^2y^2

b: (-3x+2)(5x^2-1/3x+4)

=-12x^3+x^2-12x+10x^2-2/3x+8

=-12x^3+11x^2-38/3x+8

c: =x^2-x-2+3x-x^2

=2x-2

d: =4x^2+12x+9-4x^2+25-(x-1)(x^2+12)

=12x+34-x^3-12x+x^2+12

=-x^3+x^2+46

a, \(A=2x^2+x+6\)

Với x = 1 suy ra A = 2 + 1 + 6 = 9 

Với x = 1/2 suy ra A = 1/2 + 1/2 + 6 = 7 

b, \(B=7x-6y-5\)Thay x = 3 ; y = -2 ta được 

B = 7.3 - 6 ( - 2 ) - 5 = 21 + 12 - 5 = 33 - 5 = 28 

a) x(x + 1) - 2x(x - 2) = x² + x - 2x² + 4x = -x² + 5x

b) -3x(x - 1) + (x - 1)(x + 1) = -3x² + 3x + x² - 1 = -2x² + 3x  - 1

c) (3x - 2)(3x + 2) - (x - 1)(x + 2) = 9x² - 4 - x² - x + 2 

= 8x² - x - 2

a, x(x+1) - 2x(x -2 )

= x² +x  - 2x² + 4x  = -x² + 5x

b, -3x( x - 1 ) + ( x -1 ) ( x+1 )

= -3x² + 3x + x² -1

= -2x² + 3x -1

c, ( 3x-2 ) ( 3x + 2 ) - ( x -1 ) ( x +2 )

= 9x² - 4 - ( x² + 2x -x -2 ) 

= 9x² -4 - x² -2x + x + 2

= 8x² -x -2

*Sxl

Trả lời:

a) x ( x + 1 ) - 2x ( x - 2 ) = x² + x - 2x² + 4x = - x² + 5x

b) - 3x ( x - 1 ) + ( x - 1 ) ( x + 1 ) = - 3x² + 3x + x² - 1 = - 2x² + 3x - 1

c) ( 3x - 2 ) ( 3x + 2 ) - ( x - 1 ) ( x + 2 ) = 9x² - 4 - ( x² + 2x - x - 2 ) = 9x² - 4 - x² - 2x + x + 2 = 8x² - x - 2