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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
27n/23n
= (27)n/(23)n
= 128n/8n
= (128/8)n
= 16n
Ủng hộ mk nha ^_-
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Sửa đề: Tìm n để 2n+5 chia hết cho 7n+1
=>14n+35 chia hết cho 7n+1
=>14n+2+33 chia hết cho 7n+1
=>\(7n+1\in\left\{1;-1;3;-3;11;-11;33;-33\right\}\)
=>\(n\in\left\{0;-\dfrac{2}{7};\dfrac{2}{7};-\dfrac{4}{7};\dfrac{10}{7};-\dfrac{12}{7};\dfrac{32}{7};-\dfrac{34}{7}\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{49}{81}=\dfrac{7^x}{9^x}\)(sửa đề)
\(\Leftrightarrow\left(\dfrac{7}{9}\right)^2=\left(\dfrac{7}{9}\right)^x\)\(\Rightarrow x=2\)
b) \(\dfrac{-64}{343}=\left(-\dfrac{4^x}{7^x}\right)\)(sửa đề)
\(\Leftrightarrow\left(-\dfrac{4}{7}\right)^3=\left(-\dfrac{4}{7}\right)^x\) \(\Rightarrow x=3\)
c) \(\dfrac{9}{144}=\dfrac{3^x}{12^x}\)(sửa đề)
\(\Leftrightarrow\left(\dfrac{3}{12}\right)^2=\left(\dfrac{3}{12}\right)^x\Rightarrow x=2\)
d) \(-\dfrac{1}{32}=\left(-\dfrac{1^x}{2^x}\right)\)(sửa đề)
\(\Leftrightarrow\left(-\dfrac{1}{2}\right)^5=\left(-\dfrac{1}{2}\right)^x\Rightarrow x=5\)
Mong bạn xem lại đề bài.
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(7^5:343\)
\(=7^5:7^3\)
\(=7^{5-3}\)
\(=7^2\)
b) \(a^{12}:a^{18}\)
\(=\dfrac{a^{12}}{a^{18}}\)
\(=\dfrac{a^0}{a^6}\)
\(=\dfrac{1}{a^6}\)
c) \(x^7\cdot x^4\cdot x\)
\(=x^{7+4+1}\)
\(=x^{12}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(49< 7^n< 343\)
\(7^2< 7^n< 7^3\)
→\(2< n< 3\)mà \(n\in Z\)
⇒\(n\in\varnothing\)
\(49=7^2\)
\(343=7^3\)
\(\Rightarrow7^2< 7^{ }< 7^3\)
ko có