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Warm Up. Factor Completely. 25x 2 – 36 8x 3 + 27 x 2 + 5x – 14 14y 2 – 33y – 5 x 3 – 4x 2 + 5x – 20. Evaluating Logs ( ln ) & Properties of Logs. Logarithms… Log functions and exponential functions are inverses… If f(x) = b x ,then f -1 (x) = log b x.
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Warm Up Factor Completely. 25x2 – 36 8x3+ 27 x2 + 5x – 14 14y2 – 33y – 5 x3 – 4x2 + 5x – 20
Logarithms… Log functions and exponential functions are inverses… If f(x) = bx,then f-1(x) = logbx
Logarithmic Form Exponential Form Lots of examples of switching forms…
Talk to your group… • If 101.681 = 48, what is log 48 ? _____ • If log 156 = 2.193, what is 102.193 ? __
Your Turn… Log864 = ____ Log464 = ____ Log264 = ____ Log6464 = ____ Log81 = ____ Log8 (1/64) = ____
If 52.892 = 105, then log5105 = ____ • If log217 = 4.088, what is 24.088 ? • log5(54) = ____ • = ____
Ln (read “Natural Log”) is a special log with a base e. Basic Log Properties: • ln 1 and log 1 = _____ • lne = _____ • logbb = _____ • elnx = _____ • _____
Examples: Use the properties of logs to expand. Write as a single log(condense):
Change of Base • Since our calculators can only evaluate a base of 10 or e, we will let a = 10 or use ln. • This formula allows us to evaluate logs with ANY base using the calculator!
Examples Evaluate using change of base: