February 24, 2011
Logarithmic Functions
For every exponential function, there is a logarithmic function that is its inverse.
Logarithmic Form
Exponential Form
2
3 =9
log39 = 2
3-2 = 1/9
log (1/9) = -2
3
53 = 125
Write the exponential equation in logarithmic form:
53 = 125
4-2 = 1/16
7-u = w
Write the logarithmic equation in exponential form:
log 9 = 2
3
log (1/25) = -2
5
log 9 = m
b
February 24, 2011
Evaluate the expression without a calculator:
log44
log416
log4(1/4)
log4(1/16)
log464
log4(1/64)
Evaluate each expression.
log5625
log9729
Think 5x = 625. The power must be bigger than 1.
February 24, 2011
Evaluate each expression.
log7(1/49)
log4(1/64)
x
Think 7 = 1/49.
The power must be negative to
get a reciprocal.
February 24, 2011
When a log and exponent have the same base and are applied back to
back, they cancel each other.
Evaluate the expression without a calculator:
log13169
log450
13
logm22
m
4
log77-13
logbb1.7
Assignment: "The Meaning of Logarithms" worksheet
Don't do #27, 31, or 36.