Question

I need help on a mathematics question. I need an explanation.

Solve 2 log x = log 64.

x = 8
x = ±8
x = 32
x = 128
Why is it not B and rather A? I agree with 8, but I also think that -8 works.

Answer 1

Start by dividing both sides by 2 to get $log(x)= \frac{1}{2}log(64)$.  Doing the math on the right, keeping in mind that logs have an unwritten base of 10, gives us $log_{10} (x)=.903089987$.  Rewriting this in exponential form is $10^{.903089987}=x$.  That means that x = 8.  Not negative, only positive.