Math Problem Statement

2^(x+3) =2^(1-x) + 15

Solution

Let's solve the equation 2(x+3)=2(1x)+152^{(x+3)} = 2^{(1-x)} + 15.

Step 1: Simplify the equation by isolating the exponential terms

We have: 2(x+3)=2(1x)+152^{(x+3)} = 2^{(1-x)} + 15 Subtract 2(1x)2^{(1-x)} from both sides to get: 2(x+3)2(1x)=152^{(x+3)} - 2^{(1-x)} = 15

Step 2: Express the exponents in a simpler form

Rewrite 2(x+3)2^{(x+3)} and 2(1x)2^{(1-x)}: 2(x+3)=2x23=82x2^{(x+3)} = 2^x \cdot 2^3 = 8 \cdot 2^x 2(1x)=22x2^{(1-x)} = \frac{2}{2^x} So, the equation becomes: 82x22x=158 \cdot 2^x - \frac{2}{2^x} = 15

Step 3: Multiply through by 2x2^x to eliminate the fraction

Multiply every term by 2x2^x to get: 8(2x)22=152x8 \cdot (2^x)^2 - 2 = 15 \cdot 2^x

Step 4: Introduce a substitution

Let y=2xy = 2^x. The equation now is: 8y215y2=08y^2 - 15y - 2 = 0

Step 5: Solve the quadratic equation

Use the quadratic formula: y=b±b24ac2ay = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} where a=8a = 8, b=15b = -15, and c=2c = -2: y=15±(15)248(2)16y = \frac{15 \pm \sqrt{(-15)^2 - 4 \cdot 8 \cdot (-2)}}{16} y=15±225+6416y = \frac{15 \pm \sqrt{225 + 64}}{16} y=15±28916y = \frac{15 \pm \sqrt{289}}{16} y=15±1716y = \frac{15 \pm 17}{16}

This gives two possible values for yy: y=3216=2ory=216=18y = \frac{32}{16} = 2 \quad \text{or} \quad y = \frac{-2}{16} = -\frac{1}{8}

Step 6: Solve for xx

Recall that y=2xy = 2^x. Therefore:

  • If y=2y = 2, then 2x=22^x = 2, so x=1x = 1.
  • If y=18y = -\frac{1}{8}, there's no real solution because 2x2^x is always positive.

Final Answer

The only solution is x=1x = 1.

Would you like more details or have any questions?

Here are 5 related questions you might find interesting:

  1. What is the general method for solving exponential equations?
  2. How do you solve equations involving logarithms?
  3. Can you solve 3x+2=53x1+183^{x+2} = 5 \cdot 3^{x-1} + 18?
  4. What happens when you have an exponential equation with different bases?
  5. How does the quadratic formula apply to different types of equations?

Tip: Always check for extraneous solutions, especially when dealing with exponential and logarithmic equations.

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Math Problem Analysis

Mathematical Concepts

Exponential Equations
Algebra
Quadratic Equations

Formulas

Quadratic formula: x = [-b ± √(b² - 4ac)] / 2a
Exponential rules: a^(m+n) = a^m * a^n, a^(m-n) = a^m / a^n

Theorems

Quadratic formula theorem
Properties of exponents

Suitable Grade Level

Grades 9-12