Mathematics
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OpenStudy (anonymous):
3^4x-7 =4^2x+3
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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))
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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
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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?
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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.
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OpenStudy (anonymous):
thanks!! :D