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Bài 1:
a) Ta có: \(\left(2x-1\right)^{20}=\left(2x-1\right)^{18}\)
\(\Leftrightarrow\left(2x-1\right)^{20}-\left(2x-1\right)^{18}=0\)
\(\Leftrightarrow\left(2x-1\right)^{18}\left[\left(2x-1\right)^2-1\right]=0\)
\(\Leftrightarrow\left(2x-1\right)^{18}\cdot\left(2x-2\right)\cdot2x=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{2}\\x=1\end{matrix}\right.\)
b) Ta có: \(\left(2x-3\right)^2=9\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=3\\2x-3=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=6\\2x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=0\end{matrix}\right.\)
c) Ta có: \(\left(x-5\right)^2=\left(1-3x\right)^2\)
\(\Leftrightarrow\left(x-5\right)^2-\left(3x-1\right)^2=0\)
\(\Leftrightarrow\left(x-5-3x+1\right)\left(x-5+3x-1\right)=0\)
\(\Leftrightarrow\left(-2x-4\right)\left(4x-6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{3}{2}\end{matrix}\right.\)
Bài 2:
a) \(15^{20}-15^{19}=15^{19}\left(15-1\right)=15^{19}\cdot14⋮14\)
b) \(3^{20}+3^{21}+3^{22}=3^{20}\left(1+3+3^2\right)=3^{20}\cdot13⋮13\)
c) \(3+3^2+3^3+...+3^{2007}\)
\(=3\left(1+3+3^2\right)+...+3^{2005}\left(1+3+3^2\right)\)
\(=13\left(3+...+3^{2005}\right)⋮13\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)145-5[8^2-4:15]=145-5[64-4/15]=145-5.956/15=145-956/3=-521/3
b)13^2-3[15-16^2]=13^2-3.-241=169--723=892
![](https://rs.olm.vn/images/avt/0.png?1311)
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1. 53 = 5.5.5 = 125
2. 27 = 2.2.2.2.2.2.2 = 128
3. 44 = 4.4.4.4 = 256
4. 73 = 7.7.7 = 343
6. 35 = 243
7. 26 = 64
8. 34 = 81
9. 83 = 512
11. 132 = 169
12. 112 = 121
13. 142 = 196
14. 152 = 225
16. 172 = 289
17. 182 = 324
18. 192 = 361
19. 202 = 400
21. 104 = 10000
22. 105 = 100000
23. 106 = 1000000
24. 107 = 10000000
![](https://rs.olm.vn/images/avt/0.png?1311)
mình cũng hỏi về cái này gấp nha ai biết trả lời câu nào thì trả
![](https://rs.olm.vn/images/avt/0.png?1311)
\(D=\) \(\frac{11.3^{22}.3^7-9^{15}}{\left(2.3^{14}\right).2}\)
\(=\) \(\frac{11.3^{22+7}-\left(3^2\right)^{15}}{2^2.\left(3^{14}\right)^2}\)
\(=\) \(\frac{11.3^{29}-3^{30}}{4.3^{28}}\)
\(=\) \(\frac{11.3^{29}-3^{29}.3}{4.3^{28}}\)
\(=\) \(\frac{3^{29}\left(11-3\right)}{3^{28}.4}\)
\(=\) \(\frac{3^{28}.3.8}{3^{28}.4}\)
\(=\) \(\frac{3^{28}.3.4.2}{3^{28}.4}\)
\(=\) \(6\)
Chúc bn hok tốt ~
\(D=\frac{11.3^{22}.3^7-9^{15}}{\left(2.3^{14}\right).2}\)
\(=\frac{11.3^{22+7}-\left(3^2\right)^{15}}{2^2.\left(3^{14}\right)^2}\)
\(=\frac{11.3^{29}-3^{30}}{4.3^{28}}\)
\(=\frac{11.3^{29}-3^{29}.3}{4.3^{28}}\)
\(=\frac{3^{29}\left(11-3\right)}{3^{28}.4}\)
\(=\frac{3^{28}.3.8}{3^{28}.4}\)
\(=\frac{3^{28}.3.4.2}{3^{28}.4}=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)