| Properties of Logarithms |
-- Section 4.5 -- |
| Definition of Logs | log b x = y Û x = b y |
A logarithm is an exponent. |
| Write in terms of x, y, and z. * |
| We want to write the expression such that the variables are as isolated as possible. | ||
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Solve |
Step |
Property |
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Start
with division division turns into subtraction |
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= log 3 + log x - (log y + log z) |
Take
care of multiplication next multiplication turns into addition |
log b MN = log b M + log b N |
| = log 3 + log x - log y - log z | Distribute the minus sign | Recall: log x = log 10 x |
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All variables are isolated | |
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| Write in terms of the logarithms of x, y, and z. | |
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[Solution] |
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| Write in terms of the logarithms of x, y, and z. | ![]() |
| We want to write the expression such that the variables are as isolated as possible. | |||
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Solve |
Step |
Property | |
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Start
with division division turns into subtraction |
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| Recall: | Convert radicals into exponents | ||
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Replace radicals | ||
| Exponents turn into multiplication | log b M p = p log b M | ||
| Take
care of multiplication next multiplication turns into addition |
log b MN = log b M + log b N | ||
| Do log b x2 = 2 log b x next | log b M p = p log b M | ||
| Distribute 1/3 through ( ) | |||
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All variables are isolated | ||
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Write in terms of the logarithms of x, y, and z. |
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[Solution] |
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| Evaluate the following to 3 decimals places: log 2 5 |
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Solve |
Step |
Property |
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Change of Base formula | |
| HINT: use these key strokes | log 5 ÷ log 2 [enter or =] | |
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Evaluate the following to 3 decimals places: log 5 2 |
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[Solution] |
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Tutorials and Applets by
Joe McDonald
Community College of Southern Nevada