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Mathematics 26 Online
OpenStudy (anonymous):

3^4x-7 =4^2x+3

OpenStudy (rulnick):

Is that 3^(4x-7) = 4^(2x+3)? In other words, is 4x-7 the exponent on the left side?

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

and 2x+3 is the exponent on the right

OpenStudy (rulnick):

OK, hang on a sec ...

OpenStudy (rulnick):

x = (-6 log2-7 log3) / (4 (log2-log3))

OpenStudy (rulnick):

or about 7.31

OpenStudy (anonymous):

can you explain how you got to that answer?

OpenStudy (rulnick):

When you take the log of each side you get (4x-7) log 3 = (2x-3) log 4

OpenStudy (rulnick):

Solve for x the usual way (just treat the logs as any other numbers).

OpenStudy (rulnick):

*above (2x-3) should be (2x+3), typo; didn't affect the answer

OpenStudy (rulnick):

OK? No?

OpenStudy (rulnick):

If you need it, the next step would be 4log3 x - 7log3 = 2log4 x + 3log4

OpenStudy (anonymous):

okayy! thanksss!!!!

OpenStudy (rulnick):

welcome

OpenStudy (anonymous):

wait would you divide after the last step you did?

OpenStudy (rulnick):

I would get the x terms on one side first: (4log3-2log4) x = ...

OpenStudy (rulnick):

3log4+7log3 would be the right-hand side :)

OpenStudy (rulnick):

Then divide each side by (4log3-2log4).

OpenStudy (anonymous):

thank you so much!!

OpenStudy (rulnick):

The only other trick I used that you might not see is 3log4 = 3log(2^2) = 6log2.

OpenStudy (anonymous):

thanks!! :D

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