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log_(2)(4x-3)+log_(2)(3x+5)=3

log2(4x3)+log2(3x+5)=3\log_{2}(4x-3)+\log_{2}(3x+5)=3

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Q. log2(4x3)+log2(3x+5)=3\log_{2}(4x-3)+\log_{2}(3x+5)=3
  1. Combine Logs: Use the property of logarithms that allows us to combine the two log terms on the left side of the equation into a single log term by multiplication.\newlinelog2(4x3)+log2(3x+5)=log2((4x3)(3x+5))\log_2(4x-3) + \log_2(3x+5) = \log_2((4x-3)(3x+5))
  2. Exponential Form: Since the sum of the logs is equal to 33, we can rewrite the equation in exponential form to remove the logarithm.\newlinelog2((4x3)(3x+5))=3\log_2((4x-3)(3x+5)) = 3 is equivalent to 23=(4x3)(3x+5)2^3 = (4x-3)(3x+5)
  3. Calculate Value: Calculate the value of 232^3.\newline23=82^3 = 8
  4. Set Product Equal: Set the product of the binomials equal to 88.(4x3)(3x+5)=8(4x-3)(3x+5) = 8
  5. Expand Equation: Expand the left side of the equation using the distributive property (FOIL method). \newline4x(3x)+4x(5)3(3x)3(5)=84x(3x) + 4x(5) - 3(3x) - 3(5) = 8\newline12x2+20x9x15=812x^2 + 20x - 9x - 15 = 8
  6. Combine Like Terms: Combine like terms on the left side of the equation.\newline12x2+20x9x15=812x^2 + 20x - 9x - 15 = 8\newline12x2+11x15=812x^2 + 11x - 15 = 8
  7. Set Equation to Zero: Subtract 88 from both sides to set the equation to zero.\newline12x2+11x158=012x^2 + 11x - 15 - 8 = 0\newline12x2+11x23=012x^2 + 11x - 23 = 0
  8. Quadratic Formula: Factor the quadratic equation or use the quadratic formula to find the values of xx. This equation does not factor nicely, so we will use the quadratic formula.\newlinex=b±b24ac2ax = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\newlinewhere a=12a = 12, b=11b = 11, and c=23c = -23.
  9. Calculate Discriminant: Calculate the discriminant (b24acb^2-4ac).\newlineDiscriminant = 1124(12)(23)11^2 - 4(12)(-23)\newlineDiscriminant = 121+1104121 + 1104\newlineDiscriminant = 12251225
  10. Calculate Solutions: Since the discriminant is positive, there are two real solutions. Calculate the solutions using the quadratic formula.\newlinex=11±1225212x = \frac{-11 \pm \sqrt{1225}}{2 \cdot 12}\newlinex=11±3524x = \frac{-11 \pm 35}{24}
  11. Check Validity: Calculate the two possible values for xx.x1=11+3524x_1 = \frac{{-11 + 35}}{{24}}x1=2424x_1 = \frac{{24}}{{24}}x1=1x_1 = 1x2=113524x_2 = \frac{{-11 - 35}}{{24}}x2=4624x_2 = \frac{{-46}}{{24}}x2=2312x_2 = -\frac{{23}}{{12}}
  12. Check Validity: Calculate the two possible values for x.\newlinex1=11+3524x_1 = \frac{-11 + 35}{24}\newlinex1=2424x_1 = \frac{24}{24}\newlinex1=1x_1 = 1\newlinex2=113524x_2 = \frac{-11 - 35}{24}\newlinex2=4624x_2 = \frac{-46}{24}\newlinex2=2312x_2 = \frac{-23}{12}Check the solutions in the original equation to ensure they do not result in the logarithm of a negative number or zero, as the logarithm is not defined for these values.\newlineFor x1=1x_1 = 1:\newlinelog2(4(1)3)+log2(3(1)+5)=log2(43)+log2(3+5)=log2(1)+log2(8)=0+3=3\log_2(4(1)-3) + \log_2(3(1)+5) = \log_2(4-3) + \log_2(3+5) = \log_2(1) + \log_2(8) = 0 + 3 = 3\newlineThis is valid.\newlineFor x2=2312x_2 = -\frac{23}{12}:\newlinelog2(4(2312)3)+log2(3(2312)+5)\log_2(4(-\frac{23}{12})-3) + \log_2(3(-\frac{23}{12})+5) involves the logarithm of negative numbers, which is not defined.\newlineThis is not valid.\newlineTherefore, x2=2312x_2 = -\frac{23}{12} is not a valid solution.