Math Problem Statement

Solve the following exponential equation: 5^(5x + 7) = 3^(x - 2). Express the solution in terms of natural logarithms or common logarithms. Then, use a calculator to obtain a decimal approximation for the solution.

Solution

To solve the given exponential equation:

55x+7=3x25^{5x + 7} = 3^{x - 2}

Step 1: Take the natural logarithm (ln) of both sides:

ln(55x+7)=ln(3x2)\ln(5^{5x + 7}) = \ln(3^{x - 2})

Step 2: Use the logarithmic property ln(ab)=bln(a)\ln(a^b) = b \cdot \ln(a):

(5x+7)ln(5)=(x2)ln(3)(5x + 7) \cdot \ln(5) = (x - 2) \cdot \ln(3)

Step 3: Expand both sides:

5xln(5)+7ln(5)=xln(3)2ln(3)5x \cdot \ln(5) + 7 \cdot \ln(5) = x \cdot \ln(3) - 2 \cdot \ln(3)

Step 4: Rearrange terms to isolate xx:

5xln(5)xln(3)=2ln(3)7ln(5)5x \cdot \ln(5) - x \cdot \ln(3) = -2 \cdot \ln(3) - 7 \cdot \ln(5)

Factor xx on the left-hand side: x(5ln(5)ln(3))=2ln(3)7ln(5)x \cdot (5 \cdot \ln(5) - \ln(3)) = -2 \cdot \ln(3) - 7 \cdot \ln(5)

Step 5: Solve for xx:

x=2ln(3)7ln(5)5ln(5)ln(3)x = \frac{-2 \cdot \ln(3) - 7 \cdot \ln(5)}{5 \cdot \ln(5) - \ln(3)}

Final Answer (Exact Form):

x=2ln(3)7ln(5)5ln(5)ln(3)x = \frac{-2 \ln(3) - 7 \ln(5)}{5 \ln(5) - \ln(3)}

Step 6: Use a calculator to approximate the solution:

  1. Compute the values of ln(3)\ln(3) and ln(5)\ln(5):

    • ln(3)1.0986\ln(3) \approx 1.0986
    • ln(5)1.6094\ln(5) \approx 1.6094
  2. Substitute into the equation: x=2(1.0986)7(1.6094)5(1.6094)1.0986x = \frac{-2(1.0986) - 7(1.6094)}{5(1.6094) - 1.0986}

Simplify: x2.197211.26588.0471.0986=13.4636.94841.938x \approx \frac{-2.1972 - 11.2658}{8.047 - 1.0986} = \frac{-13.463}{6.9484} \approx -1.938

Final Approximation:

x1.94x \approx -1.94

Let me know if you need further clarification or step-by-step assistance!

5 Follow-Up Questions:

  1. Would you like a detailed explanation of the logarithmic properties used?
  2. Do you want to understand how to compute natural logarithms on a calculator?
  3. Should we verify the solution by substitution into the original equation?
  4. Would you like to explore alternative methods for solving exponential equations?
  5. Are there other equations you'd like help solving?

Tip:

Always simplify logarithmic equations step-by-step and verify intermediate results to minimize errors in approximation.

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Math Problem Analysis

Mathematical Concepts

Exponential Equations
Logarithms
Algebra

Formulas

Logarithmic property: ln(a^b) = b * ln(a)
Equation solving techniques using logarithms

Theorems

Properties of Logarithms
Exponent Rules

Suitable Grade Level

Grades 10-12