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The Q is  

 (logbased3 of x)^2 - 3logbased3 of x = 10

 

Solve for x. How should I deal with this parenthesis x? Should i use the U substitution? Thanks in advanced.

 Nov 7, 2018

Best Answer 

 #1
avatar+27531 
+3

First, let y = log3(x).  Then:

 

y2 - 3y - 10 = 0

 

This factors as:  (y - 5)(y + 2) = 0

 

So y = 5 and y = -2 are solutions for y.

 

So, we have 5 = log3(x), which means x = 35

 

Also -2 = log3(x), which means x = 3-2

 Nov 7, 2018
 #1
avatar+27531 
+3
Best Answer

First, let y = log3(x).  Then:

 

y2 - 3y - 10 = 0

 

This factors as:  (y - 5)(y + 2) = 0

 

So y = 5 and y = -2 are solutions for y.

 

So, we have 5 = log3(x), which means x = 35

 

Also -2 = log3(x), which means x = 3-2

Alan Nov 7, 2018
 #2
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0

THANKS! That cleara it up! Just basic algebraic manipulation.

Guest Nov 7, 2018

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