SOLUTION: solve for x: log2x + log2(x+2)=3 the two next to the log is a little two -- this is not from a book it is from a worksheet:)

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: solve for x: log2x + log2(x+2)=3 the two next to the log is a little two -- this is not from a book it is from a worksheet:)      Log On


   

Question 35219This question is from textbook
: solve for x: log2x + log2(x+2)=3
the two next to the log is a little two --
this is not from a book it is from a worksheet:) This question is from textbook

Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
logx + log(x+2)=3 --> the logs being at base2.
log(x(x+2))=3
+x%28x%2B2%29+=+2%5E3+
+x%5E2+%2B+2x+=+8+
+x%5E2+%2B+2x+-+8+=+0+
(x+4)(x-2) = 0
so x+4=0 or x-2=0
--> x=-4, x=2

Now log(negative number) is not allowed, so although x=-4 comes out of the quadratic, it is only x=2 that is valid.


jon