My Math Forum Solving For x As An Exponent

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 March 3rd, 2016, 10:59 AM #1 Senior Member   Joined: Oct 2013 From: New York, USA Posts: 638 Thanks: 85 Solving For x As An Exponent Can somebody solve these? 1. 0.8^x = 0.5 2. 0.8^x = 0.4
 March 3rd, 2016, 11:04 AM #2 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 Do know what a logarithm is?
 March 4th, 2016, 01:45 AM #3 Senior Member   Joined: Apr 2014 From: Glasgow Posts: 2,150 Thanks: 730 Math Focus: Physics, mathematical modelling, numerical and computational solutions Yep. Taking logs of both sides is the next step. Look it up if you're not sure what they are
 March 6th, 2016, 06:32 AM #4 Senior Member   Joined: Oct 2013 From: New York, USA Posts: 638 Thanks: 85 I figured it out. I though log x^2 = 2 log x and my calculator confirmed that. Because I was rusty, I tried the reciprocal of x before finding the correct answer. It was simple to check if my answer was right.
 March 10th, 2016, 12:12 AM #5 Newbie   Joined: Mar 2016 From: Sagay City, Negros Occidental Posts: 1 Thanks: 0 Country Boy, Yes I know what logarithm is. The logarithm is the inverse operation to exponentiation. That means the logarithm of a number is the exponent to which another fixed value, the base, must be raised to produce that number. In simple cases the logarithm counts repeated multiplication.
March 10th, 2016, 12:37 AM   #6
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 Originally Posted by Sheila Guilleran Country Boy, Yes I know what logarithm is. The logarithm is the inverse operation to exponentiation. That means the logarithm of a number is the exponent to which another fixed value, the base, must be raised to produce that number. In simple cases the logarithm counts repeated multiplication.
Interesting... There seems to be a large number of users hailing from Escalante, Negros Occidental recently.

Anyways, welcome to MMF.

March 10th, 2016, 12:49 AM   #7
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 Originally Posted by Joppy Interesting... There seems to be a large number of users hailing from Escalante, Negros Occidental recently. Anyways, welcome to MMF.
They come from a few neighbouring cities on Negros Occidental... I'm guessing they're a group of friends or students in the same maths class who were encouraged to talk about maths online?

March 10th, 2016, 01:03 AM   #8
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 Originally Posted by 123qwerty They come from a few neighbouring cities on Negros Occidental... I'm guessing they're a group of friends or students in the same maths class who were encouraged to talk about maths online?

 March 10th, 2016, 02:11 AM #9 Senior Member   Joined: Apr 2014 From: Glasgow Posts: 2,150 Thanks: 730 Math Focus: Physics, mathematical modelling, numerical and computational solutions One of the most useful laws of logs is this one: $\displaystyle \log a^b = a \log b$ For example: $\displaystyle 2^x = 5$ Taking logs of both sides: $\displaystyle \log 2^x = \log 5$ Apply the law above to the left-hand side: $\displaystyle x \log 2 = \log 5$ Divide both sides by log 2: $\displaystyle x = \frac{\log 5}{\log 2}$ You can then put this into a calculator to get a decimal number if you wish. Try this technique on your questions Thanks from EvanJ

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