a) 36 459 : 9 × 3 = 4051 × 3 = 12 153

b) 14 105 x 6 : 5 = 84 630 : 5 = 16 926

a: \(A=\left(\dfrac{x}{\left(x-2\right)\left(x+2\right)}-\dfrac{2}{x-2}+\dfrac{1}{x+2}\right)\cdot\dfrac{x+2}{6}\)

\(=\dfrac{x-2x-4+x-2}{\left(x+2\right)\left(x-2\right)}\cdot\dfrac{x+2}{6}=\dfrac{-6}{6}\cdot\dfrac{1}{x-2}=\dfrac{-1}{x-2}\)

b: x=2 ko thỏa mãn ĐKXĐ

=>Loại

Khi x=3 thì A=-1/(3-2)=-1

c: A=2

=>x-2=-1/2

=>x=3/2

a: =x^3+6x^2+12x+8-(x^3+3x^2+3x+1)

=x^3+6x^2+12x+8-x^3-3x^2-3x-1

=3x^2+9x+7

b: =x^3-9x^2+27x-27-x(x^2-6x+9)

=x^3-9x^2+27x-27-x^3+6x^2-9x

=-3x^2+18x-27

c: =x^3+3x^2+3x+1-x^3-x^2-2x^2-4x

=-x+1

\(a,\left(x+2\right)^3-\left(x+1\right)^3\\ =\left(x+2-x-1\right)\left(x^2+4x+4+x^2+3x+2+x^2+2x+1\right)\\ =3x^2+9x+7\\ b,\left(x-3\right)^3-x\left(x-3\right)^2\\ =x^3-6x^2+9x-27-x^3+6x^2-9x\\ =-27\)

a) 

5 406 x 2 x 4

= 10 812 x 4 

= 43 248

b) 

370 + 9 826 + 6 530

= 10 196 + 6 530

= 16 726

a: A=(2x-1)^3

Khi x=5,5 thì A=(2*5,5-1)^3=10^3=1000

b: B=27x^3+54x^2+36x+7

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

=(3x+2)^3-1

=(-8+2)^3-1

=(-6)^3-1=-217

Bài 2:

a.

\(3x(x-4y)-\frac{12}{5}y(y-5x)=3x^2-12xy-\frac{12}{5}y^2+12xy\)

\(=3x^2-\frac{12}{5}y^2=3.4^2-\frac{12}{5}.(-5)^2=-12\)

b.

\(u=\frac{-1}{3}; v=\frac{-2}{3}\Rightarrow u+v+1=0\)

\(2u(1+u-v)-v(1-2u+v)=2u(1+u+v-2v)+v(1+u+v-3u)\)

\(=2u.(-2v)+v(-3u)=-4uv-3uv=-7uv=-7.\frac{-1}{3}.\frac{-2}{3}=\frac{-14}{9}\)

Bài 1:

\(A=x^6-(x^6-x^5)-(x^5+x^4)+(x^4-x^3)+(x^3+x^2)-(x^2+x)+1\)

\(=-x+1=-(x-1)=-(999-1)=-998\)

a) \(A=-x^3+6x^2-12x+8\)

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

\(A=-\left(x-2\right)^3\) 

Thay x=-28 vào A ta có:

\(A=-\left(-28-2\right)^3=27000\)

Vậy: ...

b) \(B=8x^3+12x^2+6x+1\)

\(B=\left(2x\right)^3+3\cdot\left(2x\right)^2\cdot1+3\cdot2x\cdot1^2+1^3\)

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

Thay \(x=\dfrac{1}{2}\) vào B ta có:
\(B=\left(2\cdot\dfrac{1}{2}+1\right)^3=8\)

Vậy: ...