log(base 2) (x+4) + log(base 2) (x+8)=5

Here's my work:

log(2) (x+4)(x+8)=10

x^2+12x+22=0

(x+11) (x+2)

-11,-2-->Answers

But my teacher said you don't use negative numbers, so what's my answer?

And, I don't know how to do this problem:

log(base 5)(2x+4) - log(base 5)(x-1)=1

My work:

log5 2(x+2)/(x-1)=5

Then what?