Example

Example: Solving a Rational Inequality with a Constant Numerator

To solve a rational inequality with a constant numerator, such as 5x22x15>0\frac{5}{x^2 - 2x - 15} > 0, first verify it is in the correct form with 00 on one side. Factoring the denominator yields 5(x+3)(x5)>0\frac{5}{(x + 3)(x - 5)} > 0. Next, determine the zero partition numbers. The quotient is 00 when the numerator is 00; however, since the numerator is the constant 55, the quotient cannot be 00. Thus, there are no zero partition numbers from the numerator. The quotient is undefined when the denominator is 00, which happens when (x+3)(x5)=0(x + 3)(x - 5) = 0, resulting in x=3x = -3 and x=5x = 5. These are the only zero partition numbers. Use 3-3 and 55 to divide the number line into intervals: (,3)(-\infty, -3), (3,5)(-3, 5), and (5,)(5, \infty). By testing values in each interval, we find where the quotient is positive. Because the inequality is strictly greater than 00, the zero partition numbers are excluded. The final solution in interval notation is (,3)(5,)(-\infty, -3) \cup (5, \infty).

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Updated 2026-05-01

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