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{:[x=17],[log_(2)(2x)+log_(2)(x-7)=log_(2)(4x)]:}

x=17log2(2x)+log2(x7)=log2(4x) \begin{array}{c}x=17 \\ \log _{2}(2 x)+\log _{2}(x-7)=\log _{2}(4 x)\end{array}

Full solution

Q. x=17log2(2x)+log2(x7)=log2(4x) \begin{array}{c}x=17 \\ \log _{2}(2 x)+\log _{2}(x-7)=\log _{2}(4 x)\end{array}
  1. Combine Logs: Combine the left side using the product rule for logarithms: log2(a)+log2(b)=log2(ab)\log_2(a) + \log_2(b) = \log_2(ab). log2(2x)+log2(x7)=log2(2x(x7))\log_2(2x) + \log_2(x - 7) = \log_2(2x \cdot (x - 7)).
  2. Simplify Left Side: Now we have log2(2x(x7))=log2(4x)\log_2(2x * (x - 7)) = \log_2(4x). Simplify the left side: 2x(x7)=2x214x2x * (x - 7) = 2x^2 - 14x.
  3. Set Equations Equal: Since the bases of the logarithms are the same, we can set the arguments equal to each other: 2x214x=4x2x^2 - 14x = 4x.
  4. Subtract and Simplify: Subtract 4x4x from both sides to get a quadratic equation: 2x214x4x=02x^2 - 14x - 4x = 0. This simplifies to 2x218x=02x^2 - 18x = 0.
  5. Factor Common Factor: Factor out the common factor of 2x2x: 2x(x9)=02x(x - 9) = 0.
  6. Set Factors Equal: Set each factor equal to zero: 2x=02x = 0 or x9=0x - 9 = 0.
  7. Solve Equations: Solve each equation: x=0x = 0 or x=9x = 9.
  8. Check Solutions: Check for extraneous solutions by plugging xx back into the original equation.\newlineFor x=0x = 0: log2(20)+log2(07)\log_2(2\cdot0) + \log_2(0 - 7) does not exist because log of a negative number is undefined.
  9. Check Solutions: Check for extraneous solutions by plugging xx back into the original equation.\newlineFor x=0x = 0: log2(20)+log2(07)\log_2(2\cdot0) + \log_2(0 - 7) does not exist because log of a negative number is undefined.For x=9x = 9: log2(29)+log2(97)=log2(49)\log_2(2\cdot9) + \log_2(9 - 7) = \log_2(4\cdot9) checks out because log2(18)+log2(2)=log2(36)\log_2(18) + \log_2(2) = \log_2(36) and 182=3618 \cdot 2 = 36.

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