-x+ 21= 15+ 2x
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
A) 149 - ( 2x - 53 ) = 54
2x - 53 = 149 - 54
2x - 53 = 95
2x = 95 + 53
2x = 148
x = 148 : 2
x = 74
B) 47 - 3( 2x - 18 ) = 35
3( 2x - 18 ) = 47 - 35
3( 2x - 18 ) = 12
2x - 18 = 12 : 3
2x - 18 = 4
2x = 4 + 18
2x = 22
x = 22 : 2
x = 11
C) 2x - 105 : 21 = 15
2x - 5 = 15
2x = 15 + 5
2x = 20
x = 20 : 2
x = 10
D) ( 2x - 105 ) : 21 = 15
2x - 105 = 15 x 21
2x - 105 = 315
2x = 315 + 105
2x = 420
x = 420 : 2
x = 210
![](https://rs.olm.vn/images/avt/0.png?1311)
\(-x+21=15+2x\)
\(\Rightarrow-x-2x=15-21\)
\(\Rightarrow-3x=-6\)
\(\Rightarrow x=2\)
\(-x+21=15+2x\)
\(-x-2x=15-21\)
\(-x+\left(-2x\right)=-6\)
\(-3x=-6\)
\(x=-6:-3\)
\(x=2\)
Vậy: x=2
![](https://rs.olm.vn/images/avt/0.png?1311)
-x + 21 = 15 + 2x
<=> -x -2x = -21 + 15
<=> -3x = -9
<=> x= 3
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
1.
b) \(3^x+3^{x+2}=2430\)
\(\Rightarrow3^x.1+3^x.3^2=2430\)
\(\Rightarrow3^x.\left(1+3^2\right)=2430\)
\(\Rightarrow3^x.10=2430\)
\(\Rightarrow3^x=2430:10\)
\(\Rightarrow3^x=243\)
\(\Rightarrow3^x=3^5\)
\(\Rightarrow x=5\)
Vậy \(x=5.\)
c) \(\left(2x-15\right)^5=\left(2x-15\right)^3\)
\(\Rightarrow\left(2x-15\right)^5-\left(2x-15\right)^3=0\)
\(\Rightarrow\left(2x-15\right)^3.\left[\left(2x-15\right)^2-1\right]=0\)
\(\Rightarrow\left[{}\begin{matrix}\left(2x-15\right)^3=0\\\left(2x-15\right)^2-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}2x-15=0\\\left(2x-15\right)^2=1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}2x=15\\2x-15=\pm1\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=15:2\\2x-15=1\\2x-15=-1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\frac{15}{2}\\2x=16\\2x=14\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\frac{15}{2}\\x=8\\x=7\end{matrix}\right.\)
Vậy \(x\in\left\{\frac{15}{2};8;7\right\}.\)
Chúc bạn học tốt!
![](https://rs.olm.vn/images/avt/0.png?1311)
-x+21=15+2x
21-15=2x+x
6=3x
x=6:3
x=2
vậy x=2
Trl:
\(-x+21=15+2x\)
\(\Rightarrow21-15=2x-x\)
\(\Rightarrow6=3x\)
\(\Rightarrow x=6:3\)
\(\Rightarrow x=2\)