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![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{1}{9}.27^n=3^n\)
\(=>\frac{27^n}{9}=3^n\)
\(=>3^n=3^n=>n=1\)
b) \(2^{-1}.2^n+4.2^n=9.2^5\)
\(=>2^{n-1}.2^2.2^n=9.2^5\)
\(=>2^{n-1}.2^{2+n}=9.2^5\)
\(=>2^{2n+1}=9.5^2\)
\(=>n=\)
Câu b đề sai hay sao ấy số xấu lắm
![](https://rs.olm.vn/images/avt/0.png?1311)
a)1/9.27^n=3^n
3^n=3^n
=>n={0;1;2;3...}
Tích nha ^_^ !!!
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{1}{2}.2^n+4.2^n=9.2^5\)
\(2^n.\left(\frac{1}{2}.4\right)=288\)
\(2^n.2=288\)
\(2^n=288:2\)
\(2^n=144\)
Suy ra n ko tìm được
Ta có :
\(\frac{1}{2}\cdot2^n+4\cdot2^n=\frac{9}{2}\cdot2^5\)
\(=>\left(\frac{1}{2}+4\right)\cdot2^n=9\cdot2^5\)
\(=>\left(\frac{1}{2}+\frac{8}{2}\right)\cdot2^n=9\cdot2^5\)
\(=>\frac{9}{2}\cdot2^n=\frac{9}{2}\cdot2^5\)
\(=>2^n=2^5\)
\(=>n=5\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2^{-1}.2^n+4.2^n=9.2^5\)
\(2^n.2=9.2^5\)
\(\Rightarrow2^n=9.2^4\)
Ko có n nhé bn
![](https://rs.olm.vn/images/avt/0.png?1311)
27^n:3^n=9
3^3n:3^n=3^2
3^(3n-n)=3^2
suy ra 3n-n=2
n(3-1)=2
n.2=2
Vậy n=2:2
n=1
còn câu sau cậu tự tính
![](https://rs.olm.vn/images/avt/0.png?1311)
2-1.2n+4.2n=9.25
=>2n-1+22.2n=9.25
=>2n-1+2n+2=9.25
=>2n-1.(23+1)=9.25
=>2n-1.9=9.25
=>2n-1=25
=>n-1=5=>n=6
Ta có: \(2^{-1}\cdot2^n+4\cdot2^n=9\cdot2^5\)
\(\Leftrightarrow2^n\cdot2^{-1}+2^n\cdot2^2=9\cdot2^5\)
\(\Leftrightarrow2^n\cdot\left(2^{-1}+2^2\right)=9\cdot2^5\)
\(\Leftrightarrow2^n\cdot\dfrac{9}{2}=9\cdot2^5\)
\(\Leftrightarrow2^n=9\cdot2^5:\dfrac{9}{2}=2^5\cdot9\cdot\dfrac{2}{9}=2^6\)
hay n=6
Vậy: n=6