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# HELP

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how do i find 87= 21^x

Feb 15, 2020

#1
+107414
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$$87= 21^x\\ ln87= ln21^x\\ ln87=x ln21\\ x=\frac{ln87}{ln21}$$

x= ln(87)/ln(21) = approx 1.4668665480402957

Feb 15, 2020
#2
+1

Melody, is there a reason you used natural log?  I used log10 and got the same answer.

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Guest Feb 15, 2020
#3
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Hi Guest,

No there is no reason, you can use any log you want.

Log 10 is an equally good alternative.

Melody  Feb 15, 2020, 9:01:19 PM
#4
+1

Thank you, Melody.  I love the new avatar.    I looked it up; it's an actual road sign in Australia.

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Guest Feb 15, 2020, 9:27:15 PM
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Thanks guest,

Yes it is a relatively common roadside, in the country anyway. :)

I actually took a photo to use here but I cannot remember if this is my photo or a different one from the internet.

Melody  Feb 15, 2020, 10:29 PM
edited by Melody  Feb 15, 2020, 10:30 PM
edited by Melody  Feb 15, 2020, 10:31 PM