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D-7 Solving Exponential Equations Using Logs Notes
WARM UP: Evaluate each expression (most can be done without a calculator 😊). If an expression is undefined, explain why.
a. 𝑙𝑜𝑔2(−2) b. ln 4 c. 𝑙𝑜𝑔510 d. 𝑙𝑜𝑔3(0) d. 𝑙𝑜𝑔1
3
(1)
Example: Use logarithms to solve each equation to the nearest thousandth. a) 2 + 5x+2 = 164 b) 7 = −1 ∙ 2.3x
c) 3 ∙ 7𝑥 + 2 = 24 d) −𝑒𝑥 + 1 = 20
e) 3 ∙ 1612 3 =+x f) 15 = −2 + 102𝑥−1 You try! g) 783 = 2 + e2x-3 h) −3 + 2 ∙ 8𝑥 = 3.27
Remember…You DO NOT always have to use logs to solve an exponential equation! Determine which equation below needs logarithms to solve it, and then solve each equation.
a. 32𝑥+5 =1
9 b. 5 ∙ 3𝑥+2 = 10 c. 25𝑥+3 = 125𝑥