Math Problem Statement

Solve for x: log(x) + log(x + 2) = 4

Solution

We need to solve the equation:

log(x)+log(x+2)=4.\log(x) + \log(x + 2) = 4.

Step-by-Step Solution:

  1. Combine the Logarithmic Terms: Using the logarithmic property log(a)+log(b)=log(ab)\log(a) + \log(b) = \log(a \cdot b), we combine the two terms: log(x)+log(x+2)=log(x(x+2)).\log(x) + \log(x + 2) = \log(x(x + 2)). This simplifies the equation to: log(x(x+2))=4.\log(x(x + 2)) = 4.

  2. Rewrite in Exponential Form: Using the property loga(b)=c    b=ac\log_a(b) = c \implies b = a^c, we rewrite: x(x+2)=104.x(x + 2) = 10^4. Since 104=1000010^4 = 10000, we now have: x(x+2)=10000.x(x + 2) = 10000.

  3. Expand and Rearrange: Expand the left-hand side: x2+2x=10000.x^2 + 2x = 10000. Rearrange into standard quadratic form: x2+2x10000=0.x^2 + 2x - 10000 = 0.

  4. Solve the Quadratic Equation: Use the quadratic formula: x=b±b24ac2a,x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, where a=1a = 1, b=2b = 2, and c=10000c = -10000. Substituting these values: x=2±224(1)(10000)2(1).x = \frac{-2 \pm \sqrt{2^2 - 4(1)(-10000)}}{2(1)}. Simplify: x=2±4+400002.x = \frac{-2 \pm \sqrt{4 + 40000}}{2}. x=2±400042.x = \frac{-2 \pm \sqrt{40004}}{2}.

  5. Approximate the Square Root: Calculate 40004\sqrt{40004}: 40004200.01.\sqrt{40004} \approx 200.01. Substituting this: x=2±200.012.x = \frac{-2 \pm 200.01}{2}.

  6. Calculate Both Solutions: x=2+200.012orx=2200.012.x = \frac{-2 + 200.01}{2} \quad \text{or} \quad x = \frac{-2 - 200.01}{2}. x=198.012=99.005orx=202.012=101.005.x = \frac{198.01}{2} = 99.005 \quad \text{or} \quad x = \frac{-202.01}{2} = -101.005.

  7. Exclude the Negative Solution: Since log(x)\log(x) is undefined for x0x \leq 0, we discard x=101.005x = -101.005.

Final Answer:

x99.005.x \approx 99.005.

Would you like further clarification or additional steps explained?


Related Questions:

  1. How do we handle equations with more than two logarithmic terms?
  2. What happens if x+2x + 2 equals zero in this scenario?
  3. How would changing the base of the logarithm affect the solution?
  4. Can logarithmic equations have multiple valid solutions?
  5. How does graphing log(x)+log(x+2)\log(x) + \log(x + 2) help visualize the solution?

Tip:

Always verify the solution by substituting it back into the original logarithmic equation to ensure it satisfies all conditions.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Algebra
Quadratic Equations

Formulas

log(a) + log(b) = log(a * b)
Quadratic equation formula: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Properties of logarithms
Quadratic formula

Suitable Grade Level

Grades 10-12