Solve Logarithmic Inequality: log₀.₂₅7 + log₀.₂₅(1/3) < log₀.₂₅(x²)

Question

\log_{0.25}7+\log_{0.25}\frac{1}{3}<\log_{0.25}x^2

x=? x=\text{?}

Video Solution

Solution Steps

00:00 Solve
00:05 This is the domain of definition
00:10 We'll use the formula for logical addition, we'll get the log of their product
00:25 Let's compare the numbers
00:35 Let's find the appropriate domain
00:50 Let's check the domain of definition to find the solution
00:55 And this is the solution to the question

Step-by-Step Solution

Let's solve the inequality step-by-step:

Step 1: Apply the sum of logarithms property.
We have:

log0.25(7×13)<log0.25(x2) \log_{0.25}\left(7 \times \frac{1}{3}\right) < \log_{0.25}(x^2)

This simplifies to:

log0.25(73)<log0.25(x2) \log_{0.25}\left(\frac{7}{3}\right) < \log_{0.25}(x^2)

Step 2: Use the property of logarithms indicating that if bases are the same and the inequality involves logb(a)<logb(b)\log_b(a) < \log_b(b), where b<1b < 1, it implies:

a>b a > b

Since 0.25<10.25 < 1, the inequality log0.25(73)<log0.25(x2)\log_{0.25}\left(\frac{7}{3}\right) < \log_{0.25}(x^2) implies:

73>x2 \frac{7}{3} > x^2

Step 3: Simplify the inequality:
x2<73 x^2 < \frac{7}{3}

Since x2<73x^2 < \frac{7}{3}, this implies:

73<x<73 -\sqrt{\frac{7}{3}} < x < \sqrt{\frac{7}{3}}

Thus, the domain of xx based on the restriction of positive numbers for logarithm and quadratic expression is:

73<x<0 and 0<x<73 -\sqrt{\frac{7}{3}} < x < 0 \text{ and } 0 < x < \sqrt{\frac{7}{3}}

Therefore, the correct solution is 73<x<0,0<x<73-\sqrt{\frac{7}{3}} < x < 0, 0 < x < \sqrt{\frac{7}{3}}.

Thus, the choice that corresponds to this solution is Choice 1.

Answer

-\sqrt{\frac{7}{3}} < x < 0,0 < x < \sqrt{\frac{7}{3}}