7-3 Logarithms Functions and Inverses
 Evaluate and Solve
Function y=2x
X
Inverse x=2y
Y
X
Y
-2
-2
-1
-1
0
1
1
0
1
2
2
1
2
4
4
2
The inverse y is called the logarithm of x. Written as y=logbx
Definition of a logarithm: b>0 b 1 Logbx=y if and only if by=x
Write each in Logarithmic form:
(ex)
Log2 16 = 4
Evaluate each Logarithm:
(ex) log9 3
log9 3 =
(ex)
(18)
Log5 625 = 4
(ex) log3 81
log3 81=x
(26) log5 (-25)
log5 (-25)=x
will never happen
undefined
Describe how the graph of each function compares with the graph of the parent function.
Logbx=y
(40) y= Log5 x+1
shift up 1 unit
(ex) y= Log7 (x-2)
shifts right 2 untis