(-123)+(409-23)-(-2017+409)=1871

Ta có: 2.3^x+3^x+2=891
         2.3^x+3^x.3^2=891
             3^x.(2+3^2)=891
                3^x.(2+9)=891
                     3^x.11=891 
                          3^x=891:11
                          3^x=81
                          3^x=3^4
                         =>x=4

Vậy x=4 
. là dấu nhân nhé 

\(2.3^x+3^{x+2}=891\)

\(3^x\left(2+3^2\right)=891\)

\(3^x.11=891\)

\(3^x=81\)

\(3^x=3^4\)

\(\Rightarrow x=4\)

( 6-x ) + (-11) = - 7

<=>6-x=(-7)-(-11)

<=>6-x=4

<=>x=6-4

<=>x=2

Vậy x=2

\(\left(x-3.4^2\right)^3=-64\)

\(\left(x-3.4^2\right)^3=-8^3\)

\(\Rightarrow x-3.4^2=-8\)

\(x-3.16=-8\)

\(x-64=-8\)

\(x=56\)

\(\left(x+4\right)⋮\left(2x+1\right)\Rightarrow2\left(x+4\right)=2x+8=2x+1+7⋮\left(2x+1\right)\Leftrightarrow7⋮\left(2x+1\right)\)

\(\Leftrightarrow2x+1\inƯ\left(7\right)=\left\{-7,-1,1,7\right\}\Leftrightarrow x\in\left\{-4,-1,0,3\right\}\).

Thử lại đều thỏa mãn. 

BCNN(10;14;18)=420 nhé

Answer:

\(x+4⋮2x+1\)

\(\Rightarrow2\left(x+4\right)⋮2x+1\)

\(\Rightarrow2x+8⋮2x+1\)

\(\Rightarrow\left(2x+1\right)+7⋮2x+1\)

Mà \(2x+1⋮2x+1\)

\(\Rightarrow7⋮2x+1\)

\(\Rightarrow2x+1\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)

\(\Rightarrow x\in\left\{0;-1;-4;3\right\}\)