x - ( 81 + 5x ) = 19

=> x - 81 - 5x = 19

=> ( x - 5x ) - 81 = 19

=> -4x = 19 + 81

=> -4x = 100

=> x = 100 : ( -4 )

=> x = -25

2x - ( 8 + 3x ) = 92

=> 2x - 8 - 3x = 92

=> ( 2x - 3x ) = 8 + 92

=> -x = 100

=> x = -100

\(\Leftrightarrow\left[{}\begin{matrix}3x-2=-18\\3x-2=18\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{16}{3}\\x=\dfrac{20}{3}\end{matrix}\right.\)

3X=9

X=3

x=3

tick mk nha bạn

x=3 
Nhớ tich mik nha bạn !

x+2x+3x+...+10x=-165

x.(1+2+3+..+10)=-165

x.55=-165

x=-3

k

x+ 2x+ 3x+ ... + 10x= -165

x. (1+ 2+ 3+ ... + 10)= -165

x. 55= -165

x= -165: 55

=> x= -3

Bạn xem có đúng không?

x + 2x + 3x +  ... + 10x = -165

55x = -165

suy ra x = -165 : 55 = -3

\(3^{x-2}=81\\ \Rightarrow3^{x-2}=3^4\\ \Rightarrow x-2=4\\ \Rightarrow x=6\)

Vậy x = 6

3^x-2=3⁴

x-2=4

x=4+2

x=6

NẾU SAI CHO MIK XIN LỖI !

Cảm ơn 2 bạn

3\(^x\) = \(\dfrac{9^4}{81^3}\)

3\(^x\) = \(\dfrac{\left(3^2\right)^4}{\left(3^4\right)^3}\)

3\(^x\) = \(\dfrac{3^8}{3^{12}}\)

3\(^x\) = 3^-4

\(x\) = -4

Vậy \(x\) = -4

x.(1+2+3+...+10) = -165

x. (11.10 : 2) = -165

x. 55 = -165

x= -165:55=-3

-3 đó mình chắc chắn luôn

\(3^x=81\)

nên x=4

x =4

\(3^x=81\)

\(\Leftrightarrow\)\(3^x=3^4\)

\(\Rightarrow\)\(x=4\)

\(\Leftrightarrow3^{x^2-5x+4}=3^4\\ \Leftrightarrow x^2-5x+4=4\\ \Leftrightarrow x\left(x-5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\)

=>3x-125=1

hay x=42

92-(3x-125).11=81

(3x-125).11=92-81

(3x-125).11=11

3x-125=11.11

3x-125=121

3x=121+125

3x=246

x=246:3

x=82