Example

Try It: Solving 13+6x2<3x\frac{1}{3} + \frac{6}{x^2} < \frac{3}{x}

To solve the rational inequality 13+6x2<3x\frac{1}{3} + \frac{6}{x^2} < \frac{3}{x}, begin by subtracting 3x\frac{3}{x} from both sides to get 00 on the right: 13+6x23x<0\frac{1}{3} + \frac{6}{x^2} - \frac{3}{x} < 0. Find the least common denominator (LCD), which is 3x23x^2, and rewrite each term to combine them into a single fraction: x23x2+183x29x3x2<0\frac{x^2}{3x^2} + \frac{18}{3x^2} - \frac{9x}{3x^2} < 0. Combine and rearrange the numerator: x29x+183x2<0\frac{x^2 - 9x + 18}{3x^2} < 0. Next, factor the numerator to obtain (x3)(x6)3x2<0\frac{(x - 3)(x - 6)}{3x^2} < 0. Determine the zero partition numbers by setting the factors of the numerator and denominator to zero. This gives x=3x = 3 and x=6x = 6 from the numerator, and x=0x = 0 from the denominator. Use the partition numbers 00, 33, and 66 to divide the number line into intervals: (,0)(-\infty, 0), (0,3)(0, 3), (3,6)(3, 6), and (6,)(6, \infty). By testing values in these intervals, determine where the expression is negative. The quotient is negative in the interval (3,6)(3, 6). Because the inequality symbol is strictly less than (<$), the partition numbers are not included. The solution in interval notation is (3, 6)$$.

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Updated 2026-05-26

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