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a) (2x-1)^3=27
b) (2x-1)^4=81
c) (x-2)^5=-32
d) (3x-1)^4=(3x-1)^6
đ) 5^x +5^x+2=650
g) 3^x-1 +5.3^x-1=162
![](https://rs.olm.vn/images/avt/0.png?1311)
a) (2x-1)3 = 27
(2x-1)3 = 93
2x-1 = 9
2x = 9+1
2x = 10
x = 10:5
x = 2
Vậy x = 2
b) (2x-1)4 = 81
(2x-1)4 = (\(\pm\)34)
2x-1 = \(\pm\)3
Trường hợp 1:
2x-1 = 3
2x = 3+1
2x = 4
x = 4:2
x = 2
Trường hợp 2:
2x-1 = -3
2x = -3+1
2x = -2
x = -2:2
x = -1
Vậy x \(\in[_{ }2;-1]\)
Vì không tìm thấy ngoặc nhọn nên mình dùng tạm ngoặc vuông nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Cho tớ sửa lại phần b nhé :
(x+2)2=81
(x+2)2=92=(-9)2
\(\Rightarrow\left[{}\begin{matrix}x+2=-9\\x+2=9\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=-11\\x=7\end{matrix}\right.\)
Vậy x\(\in\){-11;7}
a) |x-3|=5
\(\Rightarrow\left[{}\begin{matrix}x-3=-5\\x-3=5\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=-2\\x=8\end{matrix}\right.\)
Vậy x\(\in\){-2;8}
b) (x+2)2=81
(x+2)2=92
\(\Rightarrow\)x+2=9
x=9-2
x=7
Vậy x=7.
c) 5x+5x+2=650
5x+5x.52=650
5x(1+52)=650
5x.26=650
5x=650:26
5x=25
5x=52
\(\Rightarrow\)x=2
Vậy x=2.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a,\(\left(x+2\right)^2=81>0\)
\(\orbr{\begin{cases}\left(x+2\right)^2=9^2\\\left(x+2\right)^2=\left(-9\right)^2\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x+2=9\\x+2=-9\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=7\\x=-11\end{cases}}\)
a)\(\left(x+2\right)^2=81\\ =>\left(x+2\right)=9^2hay\left(x+2\right)=\left(-9\right)^2\)
x+2=9 x+2=-9
x=9-2 x=-9-2
x=7(TM) x=-11(TM)
Vậy x=7 hay x=-9
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(2x-1\right)^4=81\Rightarrow\left(2x-1\right)^4=3^4\Rightarrow2x-1=3\Rightarrow x=2\)
câu cuối này:
\(5^x+5^{x+2}=650\Rightarrow5^x\left(1+5^2\right)=650\Rightarrow5^x.26=650\)
\(\Rightarrow5^x=650:26\Rightarrow5^x=25\Rightarrow5^x=5^2\Rightarrow x=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1.
\(\left(1-2x\right)^4=81\\ \Rightarrow\left[{}\begin{matrix}1-2x=3\\1-2x=-3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}-2x=2\\-2x=-4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
Vậy ...
2.
\(\left|2,5-x\right|=1,3\\ \Rightarrow\left[{}\begin{matrix}2,5-x=1,3\\2,5-x=-1,3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1,2\\x=3,8\end{matrix}\right.\)
Vậy ...
3.
\(5^x+5^{x+2}=650\\ 5^x\left(1+5^2\right)=650\\ 5^x\cdot26=650\\ 5^x=25\\ x=2\)
Vậy ...
4, 5 tự làm
(2x+3)^2 = 4/82 = (2/9)^2
=> 2x+3 = 2/9 hoặc 2x+3 = -2/9
=> x = -25/18 hoặc x = -29/18
k mk nha