Math Problem Statement

Solve the rational inequality. Write the solution set in interval notation. StartFraction 4 Over 3 x minus 1 EndFraction greater than StartFraction negative 5 Over x EndFraction

Solution

We are tasked with solving the rational inequality:

43x1>5x\frac{4}{3x - 1} > \frac{-5}{x}

Step 1: Move all terms to one side of the inequality.

First, we subtract 5x\frac{-5}{x} from both sides to get:

43x15x>0\frac{4}{3x - 1} - \frac{-5}{x} > 0

This simplifies to:

43x1+5x>0\frac{4}{3x - 1} + \frac{5}{x} > 0

Step 2: Find a common denominator.

The least common denominator (LCD) between 3x13x - 1 and xx is x(3x1)x(3x - 1). Now, rewrite both fractions with the LCD:

4xx(3x1)+5(3x1)x(3x1)>0\frac{4x}{x(3x - 1)} + \frac{5(3x - 1)}{x(3x - 1)} > 0

Now simplify the numerator:

4x+5(3x1)x(3x1)>0\frac{4x + 5(3x - 1)}{x(3x - 1)} > 0

Expand the numerator:

4x+15x5x(3x1)>0\frac{4x + 15x - 5}{x(3x - 1)} > 0

Simplify:

19x5x(3x1)>0\frac{19x - 5}{x(3x - 1)} > 0

Step 3: Find the critical points.

The critical points occur when the numerator or denominator is zero.

  1. Numerator: 19x5=019x - 5 = 0

    Solving for xx:

    19x=5x=51919x = 5 \quad \Rightarrow \quad x = \frac{5}{19}

  2. Denominator: x(3x1)=0x(3x - 1) = 0

    Set each factor to zero:

    x=0or3x1=0x = 0 \quad \text{or} \quad 3x - 1 = 0

    Solving for xx in the second equation:

    3x=1x=133x = 1 \quad \Rightarrow \quad x = \frac{1}{3}

So, the critical points are x=0x = 0, x=13x = \frac{1}{3}, and x=519x = \frac{5}{19}.

Step 4: Analyze the sign of the expression in each interval.

The critical points divide the real number line into four intervals:

  • (,0)(-\infty, 0)
  • (0,519)(0, \frac{5}{19})
  • (519,13)\left(\frac{5}{19}, \frac{1}{3}\right)
  • (13,)\left(\frac{1}{3}, \infty\right)

Now, test a value from each interval in the expression 19x5x(3x1)\frac{19x - 5}{x(3x - 1)}:

  1. For x=1x = -1 in (,0)(- \infty, 0):

    19(1)5(1)(3(1)1)=1951(31)=244=6\frac{19(-1) - 5}{(-1)(3(-1) - 1)} = \frac{-19 - 5}{-1(-3 - 1)} = \frac{-24}{4} = -6

    This is negative.

  2. For x=110x = \frac{1}{10} in (0,519)(0, \frac{5}{19}):

    19(110)5(110)(3(110)1)=19105110(3101)\frac{19\left(\frac{1}{10}\right) - 5}{\left(\frac{1}{10}\right)(3\left(\frac{1}{10}\right) - 1)} = \frac{\frac{19}{10} - 5}{\frac{1}{10}(\frac{3}{10} - 1)}

    This simplifies to a negative value.

  3. For x=14x = \frac{1}{4} in (519,13)\left(\frac{5}{19}, \frac{1}{3}\right):

    Testing will show this is positive.

  4. For x=1x = 1 in (13,)\left(\frac{1}{3}, \infty\right):

    Testing will show this is positive.

Step 5: Write the solution in interval notation.

The expression is positive in the intervals:

(519,13)(13,)\left(\frac{5}{19}, \frac{1}{3}\right) \cup \left(\frac{1}{3}, \infty\right)

Thus, the solution set in interval notation is:

(519,13)(13,)\boxed{\left(\frac{5}{19}, \frac{1}{3}\right) \cup \left(\frac{1}{3}, \infty\right)}

Would you like more details on any of these steps?

Here are some related questions for further practice:

  1. Solve 3x21x+1\frac{3}{x - 2} \leq \frac{-1}{x + 1}.
  2. Find the solution set for 2x+3x1>4\frac{2x + 3}{x - 1} > 4.
  3. Solve x2x+12\frac{x^2}{x + 1} \geq 2.
  4. Determine the solution for 52x3<7x+2\frac{5}{2x - 3} < \frac{7}{x + 2}.
  5. Solve 4x59x+3\frac{4}{x - 5} \geq \frac{9}{x + 3}.

Tip: Always be careful when multiplying or dividing inequalities by negative values—this will flip the inequality sign.

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Math Problem Analysis

Mathematical Concepts

Algebra
Rational Inequalities
Critical Points Analysis
Interval Notation

Formulas

Finding a common denominator for rational expressions
Finding critical points by setting the numerator and denominator to zero

Theorems

Sign Analysis for Rational Expressions
Inequalities Properties

Suitable Grade Level

Grades 9-12