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

\(=x^3-6x^2+12x-8+\left(x-3\right)\left(x^2+3\right)\)

\(=x^3-6x^2+12x-8+x^3+3x-3x^2-9\)

\(=2x^3-9x^2+15x-17\)

b) Ta có: \(x\left(x-14\right)-10\left(x-1\right)^2\)

\(=x^2-14x-10\left(x^2-2x+1\right)\)

\(=x^2-14x-10x^2+20x-10\)

\(=-9x^2+6x-10\)

c) Ta có: \(2x\left(x+2\right)-\left(x+2\right)\left(x-2\right)\)

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

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

\(=x^2+4x+4\)

d) Ta có: \(\left(x-3\right)\left(x^2+3x+9\right)-\left(x^3-27\right)\)

\(=x^3-27-x^3+27\)

=0

a: \(=x^3-27-x^3-27x+x+27=-26x\)

b: \(=x^2-14x-10x^2+20x-10=-9x^2+6x-10\)

c: \(\Leftrightarrow2x^2-4x-4x^2-6x+2x+3=0\)

=>3=0(vô lý)

25 tháng 7 2021

a, `(x-3)(x^2+3x+9)-(x^2-1)(9x+27)`

`=x^3-3^3-(9x^3+27x^2-9x-27)`

`=x^3-3^3-9x^3-27x^2+9x+27`

`=-8x^3-27x^2+9x`

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

`=x^3-2^3-x(x^2-9)`

`=x^3-8-x^3+9x`

`=9x-8`

a) Ta có: \(\left(x-3\right)\left(x^2+3x+9\right)-\left(x^2-1\right)\left(9x+27\right)\)

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

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

\(=-8x^3-27x^2+9x\)

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

\(=x^3-8-x\left(x^2-9\right)\)

\(=x^3-8-x^3+9x\)

\(=9x-8\)

Bạn đăng từng bài 1 và tách bài ra cho dễ nhìn hơn nhé! 

3A:

a: =15x^4-5x^2-24x^4+18x^2-6x-6x^4+2x^3

=-15x^4+2x^3+13x^2-6x

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

=1/2x^3-1/5x^2+x-3/4x^3-5/4x^2-x

=-1/4x^3-29/20x^2

c: =3/2x^2(x^2-2x)-2x(x^3+x^2+1)+2(x-1)

=3/2x^4-3x^3-2x^4-2x^3-2x+2x-2

=-1/2x^4-5x^3-2

d: =x^4-2x^3+5x^3-10x^2+5/2x-x^4+x^3-x^2

=4x^3-11x^2+5/2x

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

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

\(b,\left(3-x\right)^3-\left(x+3\right)\left(x^2-3x+9\right)\)

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

\(c,\left(x-2\right)\left(x^2+2x+4\right)-x\left(x-3\right)\left(x+3\right)\)

\(=\left(x^3-8\right)-x\left(x^2-9\right)=x^3-8-x^3+9x=9x-8\)

26 tháng 7 2021

a) (x-3)(x2+3x+9)-(x2-1)(x+27)

=(x3-27)-(x3+27x2-x-27)

=x3-27-x3-27x2+x+27

=-27x2+x

=x(-27x+1)

b) (3-x)3-(x+3)(x2-3x+9)

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

=-2x3+9x2-27x

=x(-2x+9x-27)

c) (x-2)(x2+2x+4)-x(x-3)(x+3)

=x3-8-x(x2-9)

=x3-8-x3+9x

=9x-8

#H

22 tháng 10 2023

1:

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

\(=4x^2-20x+25-4x^2-12x\)

=-32x+25

b: \(\left(x-2\right)^3-6\left(x+4\right)\left(x-4\right)-\left(x-2\right)\left(x^2+2x+4\right)\)

\(=x^3-6x^2+12x-8-\left(x^3-8\right)-6\left(x^2-16\right)\)

\(=-6x^2+12x-6x^2+96=-12x^2+12x+96\)

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

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

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

\(=9+10x-15=10x-6\)

2: 

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

\(=9x^2-12x+4-5x^2+20x+4x-4\)

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

b: \(\left(3-x\right)\left(x^2+3x+9\right)+\left(x-3\right)^3\)

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

\(=-9x^2+27x\)

c: \(\left(x-4\right)^2\left(x+4\right)-\left(x-4\right)\left(x+4\right)^2+3\left(x^2-16\right)\)

\(=\left(x-4\right)\left(x+4\right)\left(x-4-x-4\right)+3\left(x^2-16\right)\)

\(=\left(x^2-16\right)\left(-8\right)+3\left(x^2-16\right)\)

\(=-5\left(x^2-16\right)=-5x^2+80\)

16 tháng 9 2023

A = (2x - 1)(x + 2) - 3x² + (x - 1)²

= 2x² + 4x - x - 2 - 3x² + x² - 2x + 1

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

= x - 1

B = (x - 2)(x² + 2x + 4) - (x³ + x²) - (3 - x)(3 + x)

= x³ - 8 - x³ - x² - 9 + x²

= (x³ - x³) + (-x² + x²) + (-8 - 9)

= -17

16 tháng 9 2023

A = (2x - 1)(x + 2) - 3x² + (x - 1)²

= 2x² + 4x - x - 2 - 3x² + x² - 2x + 1

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

= x - 1

B = (x - 2)(x² + 2x + 4) - (x³ + x²) - (3 - x)(3 + x)

= x³ - 8 - x³ - x² - 9 + x²

= (x³ - x³) + (-x² + x²) + (-8 - 9)

= -17

kết quả đây

chúc bạn học tốt

 

Bài 2:

a: Ta có: \(A=\left(x+1\right)^3+\left(x-1\right)^3\)

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

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

b: Ta có: \(B=\left(x-3\right)^3-\left(x+3\right)\left(x^2-3x+9\right)+\left(3x-1\right)\left(3x+1\right)\)

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

\(=27x-55\)