SOLUTION: Hello everyone! I need help with logarithmic functions please! This is a hard topic for me and could use all the help I can. Find the domain of the logarithmic function.. f(

Question 535345: Hello everyone! I need help with logarithmic functions please! This is a hard topic for me and could use all the help I can.

Find the domain of the logarithmic function..
f(x)= log(x^2-17x+72)
Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Find the domain of the logarithmic function..
f(x)= log(x^2-17x+72)
----
x^2-17x+72 must be > 0
(x-9)(x-8) > 0
---
Draw a number line and plot x=8 and x=9
---
Look for solutions in the intervals:
Try x = 0: -*- > 0 ; true, so solutions in (-oo,8)
Try x = 8.5: -*+ > 0 ; false
Try x = 9.5: +*+ > 0 ; true, so solutions in (9,+oo)
------------
Domain: (-oo,8)U(9,+oo)
============================
Cheers,
Stan H.
================
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!

" logs are exponents " That's worth repeating.
It's important how you read this equation.
is what I get when I
raise to the exponent
-------------------------------
The thing to see here is that there is no way
you can end up with a negative by raising
to some power like
so, can't be negative.
But, the log of this can be negative,
positive or zero
the domain is
- infinity < f(x) < + infinity
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