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Lời giải:
a.
ƯCLN $ =5^2=25$
BCNN $=3.5^2.7=525$
b.
ƯCLN $=3$
BCLNN $=2^2.3^2.5.7.11=13860$
![](https://rs.olm.vn/images/avt/0.png?1311)
\(3^x+3^{x+1}+3^{x+2}=117\)
\(3^x+3^x.3+3^x.3^2=117\)
\(3^x\left(1+3+3^2\right)=117\)
\(3^x.13=117\)
\(3^x=9\)
\(\Rightarrow x=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)
\(3^x+3^{x+1}+3^{x+2}=117\\ \Leftrightarrow3^x+3.3^x+9.3^x=117\\ 13.3^x=117\\ \Leftrightarrow3^x=9\\ \Leftrightarrow3^x=3^2\\ \Leftrightarrow x=2\)
b)
\(3+4\left(x-10\right)=3^2+6\\ \Leftrightarrow3+4\left(x-10\right)=15\\ \Leftrightarrow4\left(x-10\right)=12\\ \Leftrightarrow x-10=3\\ \Leftrightarrow x=13\)
a) \(3^x+3^{x+1}+3^{x+2}=117\)
\(3^x+3^x.3+3^x.3^2=117\)
\(3^x.\left(1+3+3^2\right)=117\)
\(3^x.13=117\)
\(3^x=9\)
\(x=2\)
b) \(3+4\left(x-10\right)=3^2+6\)
\(3+4x-40=9+6\)
\(4x=15+40-3\)
\(4x=52\)
\(x=13\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a/ => 1/3x = 5+4/3 = 19/3
=> x = 19/3 : 1/3 = 19
b/ 2/3x = 2-1/2 = 3/2
x = 3/2 : 2/3=9/4
c/ 3+5 = x+3/4x
8 = 7/4x
x = 8:7/4
x = 32/7
3x - 3x - 1 + 3x - 2 = 117
<=> 3x - 2 . (32 + 31 + 1)
<=> 13 . 3x - 2
<=> 3x - 2 = 117 : 13
<=> 3x - 2 = 9
<=> 3x - 2 = 32
<=> x - 2 = 2
<=> x = 2 - 2
<=> x = 2
=> x = 2
3x - 3x - 1 + 3x - 2 = 117
<=> 3x - 2 . (32 + 31 + 1)
<=> 13 . 3x - 2
<=> 3x - 2 = 117 : 13
<=> 3x - 2 = 9
<=> 3x - 2 = 32
<=> x - 2 = 2
<=> x = 2 - 2
<=> x = 2
=> x = 2