Math Problem Statement

Solve for x, giving your answer correct to two decimal places. 3^(x+1) = 5^(2x-1)

Solution

To solve the equation 3x+1=52x13^{x+1} = 5^{2x-1} for xx, let's proceed by taking the logarithm of both sides:

Step-by-Step Solution:

  1. Start with the given equation: 3x+1=52x13^{x+1} = 5^{2x-1}

  2. Take the natural logarithm of both sides: ln(3x+1)=ln(52x1)\ln(3^{x+1}) = \ln(5^{2x-1})

  3. Use the power rule of logarithms, ln(ab)=bln(a)\ln(a^b) = b \ln(a): (x+1)ln(3)=(2x1)ln(5)(x+1) \ln(3) = (2x - 1) \ln(5)

  4. Expand both sides: xln(3)+ln(3)=2xln(5)ln(5)x \ln(3) + \ln(3) = 2x \ln(5) - \ln(5)

  5. Group terms involving xx on one side and constant terms on the other side: xln(3)2xln(5)=ln(5)ln(3)x \ln(3) - 2x \ln(5) = - \ln(5) - \ln(3)

  6. Factor out xx on the left side: x(ln(3)2ln(5))=(ln(5)+ln(3))x (\ln(3) - 2 \ln(5)) = - (\ln(5) + \ln(3))

  7. Solve for xx: x=(ln(5)+ln(3))ln(3)2ln(5)x = \frac{- (\ln(5) + \ln(3))}{\ln(3) - 2 \ln(5)}

  8. Calculate the values of the logarithms:

    • ln(3)1.0986\ln(3) \approx 1.0986
    • ln(5)1.6094\ln(5) \approx 1.6094

    Substitute these values into the equation:

    x=(1.6094+1.0986)1.098621.6094x = \frac{- (1.6094 + 1.0986)}{1.0986 - 2 \cdot 1.6094}

  9. Simplify the calculations: x=2.7081.09863.2188=2.7082.12021.28x = \frac{- 2.708}{1.0986 - 3.2188} = \frac{- 2.708}{-2.1202} \approx 1.28

Final Answer:

x1.28x \approx 1.28

Would you like more details on any part of this solution, or do you have further questions?


Here are some related questions that could expand your understanding:

  1. How would the solution change if the equation was 3x+1=5x13^{x+1} = 5^{x-1}?
  2. Can you solve 3x+2=42x33^{x+2} = 4^{2x-3} using similar steps?
  3. What would happen if we used a different logarithmic base, such as base 10, instead of the natural logarithm?
  4. How can we verify the solution using substitution or graphing?
  5. What are some common mistakes to watch out for when solving exponential equations?

Tip: When solving equations involving exponents, logarithmic properties like the power rule (ln(ab)=bln(a)\ln(a^b) = b \ln(a)) are extremely useful for simplifying the expression.

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Math Problem Analysis

Mathematical Concepts

Exponential Equations
Logarithmic Properties
Algebra

Formulas

Power Rule of Logarithms: ln(a^b) = b ln(a)

Theorems

Properties of Logarithms

Suitable Grade Level

Grade 11-12