Math Problem Statement

Tell me what is x if

2^(2x+8) = 3^(x-3)

Solution

We are given the equation:

22x+8=3x32^{2x+8} = 3^{x-3}

To solve for xx, we can use logarithms. Here’s the step-by-step approach:

Step 1: Take the logarithm of both sides

We can take the natural logarithm (ln) or the logarithm to any base, but we'll use the natural logarithm for convenience:

ln(22x+8)=ln(3x3)\ln\left(2^{2x+8}\right) = \ln\left(3^{x-3}\right)

Step 2: Apply the power rule of logarithms

The power rule states that ln(ab)=bln(a)\ln(a^b) = b \ln(a). So we can rewrite both sides of the equation:

(2x+8)ln(2)=(x3)ln(3)(2x+8) \ln(2) = (x-3) \ln(3)

Step 3: Expand and rearrange terms

Now, distribute the logarithms:

(2x+8)ln(2)=(x3)ln(3)(2x+8) \ln(2) = (x-3) \ln(3)

Expanding both sides:

2xln(2)+8ln(2)=xln(3)3ln(3)2x \ln(2) + 8 \ln(2) = x \ln(3) - 3 \ln(3)

Now, collect all terms involving xx on one side of the equation:

2xln(2)xln(3)=8ln(2)3ln(3)2x \ln(2) - x \ln(3) = -8 \ln(2) - 3 \ln(3)

Step 4: Factor out xx

Factor xx from the left-hand side:

x(2ln(2)ln(3))=8ln(2)3ln(3)x \left( 2 \ln(2) - \ln(3) \right) = -8 \ln(2) - 3 \ln(3)

Step 5: Solve for xx

Now, isolate xx:

x=8ln(2)3ln(3)2ln(2)ln(3)x = \frac{-8 \ln(2) - 3 \ln(3)}{2 \ln(2) - \ln(3)}

This is the exact solution for xx. You can plug in the values of ln(2)\ln(2) and ln(3)\ln(3) to compute a numerical answer if desired:

  • ln(2)0.6931\ln(2) \approx 0.6931
  • ln(3)1.0986\ln(3) \approx 1.0986

Step 6: Final computation (optional)

Substitute the values:

x=8(0.6931)3(1.0986)2(0.6931)1.0986x = \frac{-8(0.6931) - 3(1.0986)}{2(0.6931) - 1.0986}

Now calculate:

x=5.54483.29581.38621.0986x = \frac{-5.5448 - 3.2958}{1.3862 - 1.0986}

x=8.84060.2876x = \frac{-8.8406}{0.2876}

x30.7x \approx -30.7

Final Answer:

So, x30.7x \approx -30.7.

Would you like further details on any step? Here are some questions for you:

  1. What are the properties of logarithms used in this solution?
  2. How can you use logarithms for equations involving exponents?
  3. What are some other methods for solving exponential equations?
  4. Why do we use natural logarithms in this case instead of logarithms with other bases?
  5. How would the solution change if the equation had a different base on each side?

Tip: Always double-check your calculations, especially when dealing with logarithms and exponentials, as they often involve approximation.

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Math Problem Analysis

Mathematical Concepts

Exponential Equations
Logarithms
Algebra

Formulas

Logarithm Power Rule: log(a^b) = b log(a)
Natural Logarithm (ln) Properties

Theorems

Logarithmic Identity Theorem
Properties of Exponents

Suitable Grade Level

Grades 10-12