topic badge
AustraliaVIC
VCE 11 Methods 2023

7.07 Introduction to logarithms

Worksheet
Logarithmic equations and expressions
1

Rewrite each of the following equations in exponential form:

a

\log_{4} 16 = 2

b

\log_{5} 5 = 1

c

\log_{8} 1 = 0

d

\log_{2} 0.125 = - 3

e

\log_{3} \dfrac{1}{3} = - 1

f

\log_{5.8} 33.64 = 2

g

\log_{\frac{1}{3}} 9 = - 2

h

\log_{x} 32= 5

i

\log_{8} x = 6

2

Write the following equations in logarithmic form.

a
e^{0} = 1
b
e^{x} = 3
c
e^{\frac{1}{2}} = \sqrt{e}
d
e^{p} = q
Logarithmic functions
3

Consider the function f \left( x \right) = 4 \log_{\frac{1}{4}} x.

a

Evaluate f \left( \dfrac{1}{4} \right).

b

Solve the value for x for which f \left( x \right) = 0.

4

Consider the functions f \left( x \right) = \log_{2} x + \log_{2} \left( 3 x - 4\right) and g \left( x \right) = \log_{2} \left( 4 x - 4\right).

a

Evaluate f \left( 2 \right).

b

Evaluate g \left( 2 \right).

c

Is f \left( x \right) = g \left( x \right)?

5

Consider the function f \left( x \right) = \log_{10} \left( 3 x + 9\right). Evaluate f \left( 4 \right) to two decimal places.

6

Consider the function f \left( x \right) = \log_{10} \left( - 6 x \right). Determine whether each of the following is defined. If so, evaluate the expression correct to two decimal places.

a

f \left( 3 \right)

b

f \left( \dfrac{1}{3} \right)

c

f \left( - \dfrac{1}{3} \right)

d

f \left( - 3 \right)

7

Consider the function f \left( x \right) = \log_{2}x + 3. Evaluate:

a

f \left( 8 \right)

b

f \left( \dfrac{1}{8} \right)

c

f \left( 32 \right)

d

f \left( \dfrac{1}{64} \right)

8

Suppose f \left( x \right) = \log_{a} x and f\left(2\right) = 3. Find:

a

f\left(4\right)

b

f\left(\dfrac{1}{8}\right)

c

f^{ - 1 }\left(0\right)

d

f^{ - 1 }\left( - 3 \right)

9

Consider the function f \left( x \right) = \log_{10} \left(4 x\right). Solve for the value of x for which f \left( x \right) = 2.

10

Consider the function f \left( x \right) = \log_{4} \left(k x\right) + 1. Solve for the value of k for which f \left( 4 \right) = 3.

11

After an earthquake in their home town, a family started a fund which would help cover the basic needs of those affected. People donated to the fund, and the value of the fund grew according to t = 25 \log_{14} \left(A + 1\right), where A is the amount raised (in thousands of dollars) after t days.

The family had a certain target in mind, and wanted to know how many days it would take to reach the target. They substituted A = 5000 into the formula and got the result t = 81. What do the values 5000 and 81 represent?

Natural logarithms
12

Find the value of 5 \log_{e} e.

13

Is the value of \log_{e} 2 greater than or less than 1?

14

Consider the following logarithmic expressions:

\log_{e} 7, \log_{3} 7, \log_{2} 7

Which expression has the largest value? Explain your answer.

15

Evaluate \log 23 writing the answer to the nearest thousandth.

16

Consider x=\ln 31. Find the value of x, correct to two decimal places.

17

Evaluate each of the following expressions:

a

\ln e^{3.5}

b

\ln e^{4}

c

\sqrt{6} \ln \left(e^{\sqrt{6}}\right)

d

\ln \left(\dfrac{1}{e^{2}}\right)

18

Find the exact value of x in each of the following:

a

3 \ln x = 9

b

\ln 3 x = 5

c

2 \ln 3 x = 6

d

5 e^{x} = 25

e

4 e^{x + 7} = 20

f

\ln \left( 2 x - 1\right) = \ln \left(x + 3\right)

g

\ln x + 2 = \ln \left( 2 x + 1\right)

h

e^{ - 5 \ln x } = \dfrac{1}{243}

i

\ln e^{x} - 3 \ln e = \ln e^{2}

j

e^{x + \ln 8} = 5 e^{x} + 3

k

\ln e^{\ln \left(x - 1\right)} - \ln \left(x - 7\right) = \ln 4

l

e^{ 2 x} - 8 e^{x} + 7 = 0

m

e^{ 2 x} - 7 e^{x} + 12 = 0

n

3 e^{ 2 x} - 2 e^{x} = 8

o

\dfrac{1}{3} e^{ 2 x} + 2 e^{x} = 9

p

\ln^{2} x - 4 \ln x = 5

Sign up to access Worksheet
Get full access to our content with a Mathspace account

Outcomes

U2.AoS1.18

the relationship between an exponential function to a given base and the logarithmic function to the same base as inverse functions

U2.AoS2.1

use of inverse functions and transformations to solve equations of the form Af(nx)+c, and f is sine, cosine, tangent or a^x, using exact or approximate values on a given domain

U2.AoS2.2

exponent laws and logarithm laws, including their application to the solution of simple exponential equations

What is Mathspace

About Mathspace