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July 7th, 2015, 03:52 PM  #1 
Member Joined: Jun 2015 From: Casablanca Posts: 47 Thanks: 3  How to perform log base 4 in win scientific calculator?
I solved this exercise: $\log_4 (x^2 +15)=3$, where $x=\pm7$. Then I wanted to check if both numbers were solution, with the help of windows scientific calculator, but till now I don't know how. Could you show me? Thank you. Last edited by skipjack; July 7th, 2015 at 06:14 PM. 
July 7th, 2015, 04:02 PM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,599 Thanks: 2587 Math Focus: Mainly analysis and algebra 
Use the fact that $\log_b a ={ \log_c a \over \log_c b}$

July 7th, 2015, 04:09 PM  #3 
Member Joined: Jun 2015 From: Casablanca Posts: 47 Thanks: 3  Wow, it works! Thanks.
Last edited by Mohajir; July 7th, 2015 at 04:20 PM. 

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