With the given information, you are right.
How would I solve...
9 = log_{2}x^{2 }Surely that means 2^9=x^2=512
So x=+-(sqrt)512??
But that's not the answer in the book, it gets x=+-3??
Sorry for not using Latex, I'm not too familiar with it but these are simple equations so I hope it doesn't pose too much of an issue.