February 15, 2013
Alg 2 3-5
Find without using a calculator
1. log5 125
5.
log17 1
2. log3 1/27
6. log 100
10 Is the graph of y
3. log4 42
7. log .1
8. log 0
4. log4 410
9. log (-10)
= e.5x exponential growth, or decay?
February 15, 2013
p. 490?
February 15, 2013
February 15, 2013
Yesterday we learned what a logarithm is.
if ab = c, then loga c = b
exponential form
log form
To find a if loga 36 = 2, we could put it in to exponential form.
a must be positive, and not equal to 1.
We can't take the log of a negative. Why?
The log of a number may end up being negative. Give an
example of this.
February 15, 2013
We established loga 1 = 0
loga a = 1
loga ax = x
And that 10 is the common base for the logarithm. We write
log a when we mean log10 a
So log 100 =
log 1,000 =
log 1,000,000 =
log .1=
log 1/100 =
February 15, 2013
Another base that is used often is e. It has many uses in
science and other fields.
loge 18 is written ln 18. Can you approximate this without
using a calculator? Use your calculator to see how close you
were.
ln e=
ln e5 =
February 15, 2013
Here's a tricky one:
9
log915
e
ln 234
=
=
find in terms of x : log4 16x
February 15, 2013
Find:
log25 5
log25 125 =
log16 32 =
February 15, 2013
#3-5 p. 490 18-46 even, 48-55 all,
78, 88-91