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Intermediate Algebra – Student Workbook – Second Edition 2013

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Lesson 4b <strong>–</strong> More on Logarithms<br />

Mini-Lesson<br />

Problem 3<br />

YOU TRY <strong>–</strong> COMPUTE LOGARITHMS USING CHANGE OF BASE<br />

FORMULA<br />

Use the Change of Base formula given on the previous page, and your calculator, to compute<br />

each of the following. The first one is done for you.<br />

a) log 3<br />

8<br />

Compute<br />

b) log 5<br />

41<br />

Rewrite using Change of Base<br />

log(8)<br />

log(3)<br />

Final Result (3 decimal places) <strong>–</strong><br />

Be sure to use ( ) with each logarithm<br />

separately<br />

1.893<br />

c) log 8<br />

12<br />

d) log 1.5<br />

32<br />

e) 12.8+ log 3<br />

25<br />

Solving Exponential Equations <strong>Algebra</strong>ically and Graphically<br />

We will use what we now know about Logarithmic and Exponential forms and Change of Base<br />

formula to help us solve Exponential Equations. There is a step-by-step process to solve these<br />

types of equations.<br />

Solving Exponential Equations <strong>–</strong> <strong>Algebra</strong>ically and Graphically<br />

Solving exponential equations involves these steps:<br />

ISOLATE the exponential part of the equation<br />

Change the equation to LOGARITHMIC form<br />

ISOLATE the variable<br />

IDENTIFY the final result in EXACT form then in rounded form as indicated by the<br />

problem. You may need to use Change of Base here to compute your logarithm.<br />

CHECK your result by using the graphing (intersection) method to solve the original<br />

problem<br />

Notes:<br />

<br />

<br />

To ISOLATE means to manipulate the equation using addition, subtraction,<br />

multiplication, and division so that the exponential part and its input expression are by<br />

themselves.<br />

EXACT FORM for an answer means an answer that is not rounded until the last step.<br />

Scottsdale Community College Page 165 <strong>Intermediate</strong> <strong>Algebra</strong>

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