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log4 (2x-1)+log4 3=log4 (5x+12)

 Aug 28, 2014

Best Answer 

 #2
avatar+33661 
+5

Not quite!

 

log4(2x-1) + log4(3) = log4((2x-1)*3)

So we should have

 

(2x-1)*3 = 5x+12

6x - 3 = 5x + 12

x = 15

 

Check:

$${{log}}_{{\mathtt{4}}}{\left({\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{15}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}{\mathtt{\,\small\textbf+\,}}{{log}}_{{\mathtt{4}}}{\left({\mathtt{3}}\right)} = {\mathtt{3.221\: \!471\: \!747\: \!924\: \!364\: \!5}}$$

$${{log}}_{{\mathtt{4}}}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{15}}{\mathtt{\,\small\textbf+\,}}{\mathtt{12}}\right)} = {\mathtt{3.221\: \!471\: \!747\: \!924\: \!364\: \!4}}$$

 Aug 29, 2014
 #1
avatar
0

same log base so rewrite 

2x-1 + 3 = 5x+12 

combine like terms 

2x+2=5x+12 

get x by it self 

3x=10 

solve for x 

x = 10/3 

 Aug 28, 2014
 #2
avatar+33661 
+5
Best Answer

Not quite!

 

log4(2x-1) + log4(3) = log4((2x-1)*3)

So we should have

 

(2x-1)*3 = 5x+12

6x - 3 = 5x + 12

x = 15

 

Check:

$${{log}}_{{\mathtt{4}}}{\left({\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{15}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}{\mathtt{\,\small\textbf+\,}}{{log}}_{{\mathtt{4}}}{\left({\mathtt{3}}\right)} = {\mathtt{3.221\: \!471\: \!747\: \!924\: \!364\: \!5}}$$

$${{log}}_{{\mathtt{4}}}{\left({\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{15}}{\mathtt{\,\small\textbf+\,}}{\mathtt{12}}\right)} = {\mathtt{3.221\: \!471\: \!747\: \!924\: \!364\: \!4}}$$

Alan Aug 29, 2014

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