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Ch. 4 - Exponential and Logarithmic Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 47

Solve each exponential equation in Exercises 23–48. Express the solution set in terms of natural logarithms or common logarithms. Then use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. 32x+3x−2=0

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1
Start by recognizing that the equation involves exponential expressions with the same base: \(3^{2x} + 3^x - 2 = 0\). Notice that \$3^{2x}$ can be rewritten as $(3^x)^2$.
Introduce a substitution to simplify the equation. Let \(y = 3^x\). Then the equation becomes \(y^2 + y - 2 = 0\).
Solve the quadratic equation \(y^2 + y - 2 = 0\) using the quadratic formula: \(y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\), where \(a=1\), \(b=1\), and \(c=-2\).
After finding the values of \(y\), recall that \(y = 3^x\). Solve for \(x\) by taking the logarithm of both sides: \(x = \log_3(y)\). You can express this using natural logarithms as \(x = \frac{\ln(y)}{\ln(3)}\) or common logarithms as \(x = \frac{\log(y)}{\log(3)}\).
Evaluate the logarithmic expressions using a calculator to find the decimal approximations of \(x\), rounding to two decimal places as required.

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