9^5-2x bằng 729
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\(9^{5-2x}=729\)
\(9^{5-2x}=3\)
\(5-2x=3\)
\(2x=5-3\)
\(2x=2\)
\(x=2:2\)
\(x=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
5x+1 - 5x = 100
5x. 5 - 5x . 1 = 100
5x . ( 5 - 1 ) = 100
5x . 4 = 100
5x =100 : 4
5x = 25
5x= 52
=> x = 2
2)
92x : 9 = 729
92x : 91 = 729
92x-1 = 729
92x-1 = 93
=> 2x - 1 = 3
2x = 3 + 1
2x = 4
=> x = 4 : 2
x = 2
MÌNH LÀM CÂU 2 THÔI NHÉ
92X:9=729
92X=729:9
92X=81
92X=92
SUY RA; 2.X=2
X=2:2
X=1
Vậy x=1
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 92x : 9 =729 <---> 92x=729.9 <--->92x=6561 <---->92x=92.2--->x=2
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\(9^{2x-1}=729=9^3\Leftrightarrow2x-1=3\Leftrightarrow2x=4\Leftrightarrow x=2\)
Trả lời :............................................
\(9^{2x-1}=729=9^3\Leftrightarrow2x-1=3\Leftrightarrow2x=4\Leftrightarrow x=2\)
Hk tốt,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
k nhé Kiet nguyen
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= 9 * ( x + 5 ) = 729
= ( 729 : 9 ) - 5 = x
= 81 - 5 = x
= 76 = x
Vậy x = 76
Thử : 9 * ( 76 + 5 ) = 729
= 9 * 81 = 729
Đáp số : 76
![](https://rs.olm.vn/images/avt/0.png?1311)
b. 9 × ( x + 5 ) = 729
x + 5 = 729 : 9
x + 5 = 81
x = 81 – 5
x =76
![](https://rs.olm.vn/images/avt/0.png?1311)
b. 9 × ( x + 5 ) = 729
x + 5 = 729 : 9
x + 5 = 81
x = 81 – 5
x =76
\(9^5-2x=729\)
\(\Rightarrow9^5-2x=9^3\)
\(\Rightarrow2x=9^3\times\left(9^2-1\right)\)
\(\Rightarrow2x=9^3\times80\)
\(\Rightarrow2x=58320\)
\(\Rightarrow x=\text{29160}\)
~Std well~
P/s: Chắc sai :v