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  1. Home
  2. 12th grade
  3. Algebra II
  4. Exercise : Solve equations of the form a^x=b

Solve equations of the form a^x=b Algebra II

Find the eventual solution(s) of the following equations.

3^x=24

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to 3^x=24 is found by taking the natural log of both sides:

x\cdot \ln\left(3\right)=\ln\left(24\right)

Dividing both sides by \ln\left(3\right) gives:

x=\dfrac{\ln\left(24\right)}{\ln\left(3\right)}

The solution is x=\dfrac{\ln\left(24\right)}{\ln\left(3\right)}

2^x=19

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to 2^x=19 is found by taking the natural log of both sides:

x\cdot \ln\left(2\right)=\ln\left(19\right)

Dividing both sides by \ln\left(2\right) gives:

x=\dfrac{\ln\left(19\right)}{\ln\left(2\right)}

The solution is x=\dfrac{\ln\left(19\right)}{\ln\left(2\right)}.

10^x=73

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to 10^x=73 is found by taking the natural log of both sides:

x\cdot \ln\left(10\right)=\ln\left(73\right)

Dividing both sides by \ln\left(10\right) gives:

x=\dfrac{\ln\left(73\right)}{\ln\left(10\right)}

The solution is x=\dfrac{\ln\left(73\right)}{\ln\left(10\right)}.

\left(\dfrac{1}{2}\right)^x=70

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to \left(\dfrac{1}{2}\right)^x=70 is found by taking the natural log of both sides:

x\cdot \ln\left(\dfrac{1}{2}\right)=\ln\left(70\right)

Dividing both sides by \ln\left(\dfrac{1}{2}\right) gives:

x=\dfrac{\ln\left(70\right)}{\ln\left(\dfrac{1}{2}\right)}=-\dfrac{\ln\left(70\right)}{\ln\left(2\right)}

The solution is x=-\dfrac{\ln\left(70\right)}{\ln\left(2\right)}.

\left(\dfrac{1}{3}\right)^x=81

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to 3^{-x}=81 is found by taking the natural log of both sides:

-x\cdot \ln\left(3\right)=\ln\left(81\right)

Dividing both sides by -\ln\left(3\right) gives:

x=-\dfrac{\ln\left(81\right)}{\ln\left(3\right)}=-4

The solution is x=-4.

\pi^x=50

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to \pi^x=50 is found by taking the natural log of both sides:

x\cdot \ln\left(\pi\right)=\ln\left(50\right)

Dividing both sides by \ln\left(\pi\right) gives:

x=\dfrac{\ln\left(50\right)}{\ln\left(\pi\right)}

The solution is x=\dfrac{\ln\left(50\right)}{\ln\left(\pi\right)}.

10^x=99

Solving a^x=b requires taking the log (with any base) of both sides. Using natural log, the equation becomes:

\ln\left(a^x\right)=\ln\left(b\right)

x\cdot \ln\left(a\right)=\ln\left(b\right)

Therefore, the solution to 10^x=99 is found by taking the natural log of both sides:

x\cdot \ln\left(10\right)=\ln\left(99\right)

Dividing both sides by \ln\left(3\right) gives:

x=\dfrac{\ln\left(99\right)}{\ln\left(10\right)}

The solution is x=\dfrac{\ln\left(99\right)}{\ln\left(10\right)}.

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See also
  • Course : Exponential and logarithmic equations and inequalities
  • Exercise : Convert from logarithmic form to exponential form
  • Exercise : Solve equations of the form x^a=b
  • Exercise : Solve inequalities of the form a^x > or < b
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