Solve log₄(9x) + log₄(x+4) - log₄(3) = ln(2e) + ln(1/2e): Finding X

Question

log49x+log4(x+4)log43=ln2e+ln12e \log_49x+\log_4(x+4)-\log_43=\ln2e+\ln\frac{1}{2e}

Find X

Video Solution

Solution Steps

00:00 Find X
00:06 We'll use the formula for logical addition, we'll get the log of their product
00:16 We'll use this formula in our exercise
00:41 We'll use the formula for logical subtraction, we'll get the log of their quotient
00:46 We'll use this formula in our exercise
00:54 Let's simplify what we can
01:01 We'll use the formula to convert from ln to log
01:20 We'll use this formula in our exercise
01:33 Let's simplify as much as possible
01:43 Open parentheses properly, multiply by each factor
01:53 Let's arrange the equation
02:18 We'll use the root formula to find possible solutions
02:33 Let's calculate and solve
03:38 Let's find the domain
03:55 This is the complete domain
04:02 Always remember there are 2 possibilities, addition and subtraction
04:06 This is the domain, with it we'll find the solution
04:14 And this is the solution to the question

Step-by-Step Solution

To solve this logarithmic equation, we will simplify both sides using logarithm properties.

Step 1: Combine the logarithms on the left side.

The left side is log49x+log4(x+4)log43 \log_4 9x + \log_4 (x+4) - \log_4 3 . Using the properties of logarithms, we can combine these logs:

log4(9x(x+4)3)\log_4 \left( \frac{9x(x+4)}{3} \right)

This simplifies to:

log4(3x(x+4))\log_4 \left(3x(x+4)\right)

Step 2: Simplify the right side.

The right side is ln2e+ln12e \ln 2e + \ln \frac{1}{2e} . Using properties of natural logarithms, combine as follows:

ln(2e12e)=ln1=0\ln \left(2e \cdot \frac{1}{2e}\right) = \ln 1 = 0

Step 3: Equating both sides, we have:

log4(3x(x+4))=0\log_4 \left(3x(x+4)\right) = 0

Step 4: Convert the logarithmic equation to an exponential equation. Since the logarithmic expression equals zero, it signifies:

3x(x+4)=40=13x(x+4) = 4^0 = 1

Step 5: Solve the equation 3x(x+4)=13x(x+4) = 1:

Combine and expand the terms:

3x2+12x1=03x^2 + 12x - 1 = 0

Step 6: Solve the quadratic equation using the quadratic formula x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, where a=3a = 3, b=12b = 12, and c=1c = -1:

x=12±1224×3×(1)2×3x = \frac{-12 \pm \sqrt{12^2 - 4 \times 3 \times (-1)}}{2 \times 3}

Calculate:

x=12±144+126x = \frac{-12 \pm \sqrt{144 + 12}}{6}

x=12±1566x = \frac{-12 \pm \sqrt{156}}{6}

x=12±4×396x = \frac{-12 \pm \sqrt{4 \times 39}}{6}

x=12±2396x = \frac{-12 \pm 2\sqrt{39}}{6}

x=6±393x = \frac{-6 \pm \sqrt{39}}{3}

Thus, the solution is:

x=2+393x = -2 + \frac{\sqrt{39}}{3}

This matches the correct choice.

Therefore, the solution to the problem is 2+393-2+\frac{\sqrt{39}}{3}.

Answer

2+393 -2+\frac{\sqrt{39}}{3}