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Logarithms. By: Lulu Huang, Alison Li,Gladi Pang Period 4. Product Property : log b XY = log b X + log b Y Quotient Property : log b X = log b X - log b Y Y Power property : log b X y = y logbX. 8-4 Properties of Logarithms.
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Logarithms By: Lulu Huang, Alison Li,Gladi Pang Period 4
Product Property: logbXY = logbX + logbY Quotient Property : logbX = logbX - logbY Y Power property: logbXy = ylogbX 8-4 Properties of Logarithms
8-4 Identifying Properties • Example 1:log5 + log6 = log 30 • product property • Example 2: log55 + log520 - log 54 = log525 • product and quotient property
Example 1: log44 + log432 = log4 (4 x 32) = log4132 Example 2:log 7X + log7Y - log 7Z = log 7 (X x Y) Z = log 7 XY Z 8-4 Simplifying Logarithms
Example 1:log5XY = log5X + log 5Y Example 2:log3m4n-2 = log3 + logm4 +logn-2 = log3 + 4logm + -2logn 8-4 Expanding Logarithms
Example 1:72X = 25 log72X = log25 2Xlog7 = log25 log7 log 7 2X = 1.65422 2 X = 0.8271 Example 2:202X+1 = 260 log202X+1 = log260 2X+1log20 = log260log 20 log 20 2X+1 = 1.8562 -1 -1 2X = 0.85622 2 X = 0.4281 8-5 Solving Exponential Equation
Change Of Base Formula:logaN = log Nlog a Example 1: log333 = log33log 3Example 2:log5135 = log135log5 8-5 Using Change Of Base Formula
Example 1: 2X = 5 log22X = log25 Xlog22 = log25 Xlog2 = log5log2 log2 X = 2.322 Example 2:73X+4 = 79 log773X+4 = log779 3X + 4 log7 = log79log7 log7 3X + 4 = 2.2455 -4 -4 3X = -1.75453 3 x = -0.584 8-5 Solving Exponential Equations by Changing Base
Example 1: log2X = 5 10log 2X = 105 2X = 105 2X = 10000 2 2 X = 50000 Example 2: 2log X = 2 log X2 = 2 10log X2 = 102 X2 = 102 X = 1002 X = 10000 8-5 Solving a Logarithmic Equations 2 X2 1002 =
Example 1:log X - log 3 = 3 log X = 3 3 10logX = 103 3 3 x X = 1000 (3)3 X = 3000 Example 2: log2 X - log2 6 + log2 2 = 3 log 22X = 3 6 2 log22X = 23 6 6 x 2X = 8 (6)6 2X = 482 2 X = 24 8-5 Using Logarithmic Properties to Solve Equation
Example 1: 3 ln 5 ln 53 = ln125 = 4.83 Example 2:ln a - 2 ln b + 2 ln c = ln a - ln b2 + ln c2 = ln a x c2 b2 = ln ac2 b2 8-6 Simplifying Natural Logarithms
Example 1: ln 3X = 6 e ln 3X = e6 3X = 403.433 3 X = 134.48 Example 2:1.1 + ln 2X = 12-1.1 - 1.1 ln 2X = 10.9 e ln 2X = e10.9 2X = 54176.3642 2 X = 27088.182 8-6 Solving Natural Logarithmic Equations
Example 1:eX = 5 ln e X= ln 5 X = 1.609 Example 2:2e2x - 7 = 53+7 +7 2e2X = 602 2 e2X = 30 ln e2x = ln 30 2X = 3.40122 2 X = 1.7006 8-6 Solving Exponential Equations