Solve: log₁/₃(e²ln x) < 3log₁/₃(2) Logarithmic Inequality

Question

\log_{\frac{1}{3}}e^2\ln x<3\log_{\frac{1}{3}}2

Video Solution

Solution Steps

00:00 Solve
00:07 Convert between logs
00:17 Use the logarithm product formula, switch between bases
00:27 Use the power property of logarithms, raise the number by the coefficient
00:38 Again use the formula and extract the power
00:48 Use the power property of logarithms, raise the number by the coefficient
00:53 Compare the logarithm numbers
01:13 Isolate X
01:18 Find the appropriate domain
01:23 Check the domain of definition and find the solution
01:33 And this is the solution to the problem

Step-by-Step Solution

To solve this problem, we'll follow these key steps:

  • Separate the components inside the logarithm using the property: logb(ac)=logb(a)+logb(c)\log_b(a \cdot c) = \log_b(a) + \log_b(c).
  • Apply the power property: logb(ac)=clogb(a)\log_b(a^c) = c\log_b(a).
  • Simplify the inequality and solve it.

Consider the inequality given:

log13(e2lnx)<3log13(2) \log_{\frac{1}{3}}(e^2\ln x) < 3\log_{\frac{1}{3}}(2)

Using the product property of logarithms, we can rewrite this as:

log13(e2)+log13(lnx)<3log13(2) \log_{\frac{1}{3}}(e^2) + \log_{\frac{1}{3}}(\ln x) < 3\log_{\frac{1}{3}}(2)

Next, apply the power property to simplify log13(e2)\log_{\frac{1}{3}}(e^2):

2log13(e)+log13(lnx)<3log13(2) 2\log_{\frac{1}{3}}(e) + \log_{\frac{1}{3}}(\ln x) < 3\log_{\frac{1}{3}}(2)

Let a=log13(e) a = \log_{\frac{1}{3}}(e) and b=log13(2) b = \log_{\frac{1}{3}}(2) . The inequality becomes:

2a+log13(lnx)<3b 2a + \log_{\frac{1}{3}}(\ln x) < 3b

Rearrange to isolate log13(lnx)\log_{\frac{1}{3}}(\ln x):

log13(lnx)<3b2a \log_{\frac{1}{3}}(\ln x) < 3b - 2a

Since 13\frac{1}{3} is less than 1, meaning the inequality reverses when converting back to exponential form:

lnx>(13)(3b2a) \ln x > \left(\frac{1}{3}\right)^{(3b - 2a)}

Converting the expression on the right-hand side to exponential form:

lnx>(13)log13(8) \ln x > (\frac{1}{3})^{\log_{\frac{1}{3}}(8)}

This simplifies to:

lnx>18 \ln x > \frac{1}{8}

Take the exponential of both sides to solve for xx:

x>e18 x > e^{\frac{1}{8}}

Simplifying gives:

x>8 x > \sqrt{8}

Therefore, the solution to the problem is 8<x \sqrt{8} < x .

Answer

\sqrt{8} < x