Question

Solve logarithm Equation: log2 (12b - 21) - log2 (b^2 - 3)=2

Answer 1

Hn, well you should use the rule to answer this.. $log_a(n)-log_a(m)=log_a (\frac{n}{m} )$
Sorry if this doesn't seem to help, but here is the explanation: 
$log_2 (\frac{12b-21}{b^2-3} )=2$
$\frac{12b-21}{b^2-3} =4$
$12b-21=4(b^4-3)$
$0=4b^2-12b-12+21$
$0=4b^2-12b+9$
$0=4b^2-6b-6b+9$
$0=2b(2b-3)-3(2b-3)$
$0=(2b-3)(2b-3)$
$b= \frac{3}{2}$
Hn, so from this information we can determine that this solution does not work. And so forth your solution set shall indeed be: {x= 0}

I wish you good luck on your homework and hopefully I was somewhat beneficial to your needs. 

Best regards~ Sans