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Solve log base 2 of x plus log base 2 of (x - 2) = 3

Worked through step by step. More algebra.

Answer
4\boxed{4}

Substituting x=4x = 4 back into the original equation gives log⁡2(4)+log⁡2(2)=2+1=3\log_2(4) + \log_2(2) = 2 + 1 = 3, which is correct.

Problem: Solve for xx: log⁡2(x)+log⁡2(x−2)=3\log_2(x) + \log_2(x - 2) = 3

Steps

  1. Combine logarithms using the product rule
    log⁡2(x(x−2))=3\log_2(x(x - 2)) = 3
  2. Rewrite the logarithmic equation as an exponential equation
    x(x−2)=23x(x - 2) = 2^3
  3. Simplify the right side
    x(x−2)=8x(x - 2) = 8
  4. Distribute on the left side
    x2−2x=8x^2 - 2x = 8
  5. Subtract 8 from both sides to form a quadratic equation
    x2−2x−8=0x^2 - 2x - 8 = 0
  6. Factor the quadratic equation
    (x−4)(x+2)=0(x - 4)(x + 2) = 0
  7. Solve for xx
    x=4orx=−2x = 4 \quad \text{or} \quad x = -2
  8. Check for extraneous solutions in the original domain (x>2x > 2)
    For x=−2,log⁡2(−2) is undefined, so x=−2 is rejected. For x=4, both terms are valid.\text{For } x = -2, \log_2(-2) \text{ is undefined, so } x = -2 \text{ is rejected. For } x = 4, \text{ both terms are valid.}

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