SOLUTION: write the expression (log base of b)(2y+5)-4(log base of b)(y+3) as a single logarithm

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Question 380916: write the expression (log base of b)(2y+5)-4(log base of b)(y+3) as a single
logarithm

Answer by Theo(13342)   (Show Source): You can put this solution on YOUR website!
that expression would be shown as:

log(b,(2y+5)) - 4*log(b,(y+3))

in general x * log(y) = log(y^x)

your expression becomes:

log(b,(2y+5)) - log(b,((y+3)^4))

in general log(x) - log(y) = log(x/y)

your expression becomes:

log(b,((2y+5)/(y+3)^4))

to show you how this works, we will let b = 10 because your calculator can do logs to the base of 10 (usually called the LOG function).

we will let y = 5 (chosen at random small enough to calculate easily).

your original expression becomes:

log(2y+5) - 4*log(y+3)

the base of 10 is implied.

substituting 5 for y, we get:

log(2*5+5) - 4*log(5+3) which becomes:

log(15) - 4*log(8) which becomes -2.436268689

looking at our final expression of:

log(b,(2y+5)/(y+3)^4), we get:

log((2y+5)/(y+3)^4).

the base of 10 is implied.

substituting 5 for y, we get:

log(15/8^4) which becomes log(15/4096).

using our calculator, we get log(15/4096) = log(.003662109) which equals -2.436268689

we get the same answer either way, so the translation is good, and the answer to your question is:

log(b,2y+5) - 4*log(b,y+3) = log(b,(2y+5)/(y+3)^4) which looks like:




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