3^х=7^х/2
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11 января 2025 07:25
To solve the equation ( 3^x = \frac{7^x}{2} ), we can start by rearranging it:
Multiply both sides by 2 to eliminate the fraction: [ 2 \cdot 3^x = 7^x ]
Next, let's express both sides with the same base if possible. However, since ( 3 ) and ( 7 ) don't share a common base, we can take the logarithm on both sides (we can use natural logarithm ( \ln ) or common logarithm ( \log )). Here, I’ll use natural logarithm ( \ln ):
[ \ln(2 \cdot 3^x) = \ln(7^x) ]
Using the properties of logarithms (specifically ( \ln(a \cdot b) = \ln a + \ln b ) and ( \ln(a^b) = b \cdot \ln a )), we can rewrite the equation:
[ \ln 2 + x \ln 3 = x \ln 7 ]
Now, to isolate ( x ), move all terms involving ( x ) to one side:
[ \ln 2 = x \ln 7 - x \ln 3 ]
[ \ln 2 = x (\ln 7 - \ln 3) ]
Now, divide both sides by ( \ln 7 - \ln 3 ) (assuming ( \ln 7 \neq \ln 3 )):
[ x = \frac{\ln 2}{\ln 7 - \ln 3} ]
This gives the value of ( x ) as:
[ x \approx \frac{\ln 2}{\ln 7 - \ln 3} ]
You can calculate this value using a scientific calculator or computational tool:
- Using ( \ln 2 \approx 0.693 )
- ( \ln 7 \approx 1.946 )
- ( \ln 3 \approx 1.099 )
So:
[ x \approx \frac{0.693}{1.946 - 1.099} \approx \frac{0.693}{0.847} \approx 0.819 ]
Thus, the approximate solution for ( x ) is ( x \approx 0.819 ).
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