Example

Try It: Solving 3x2+x12>0\frac{3}{x^2 + x - 12} > 0

To solve the rational inequality 3x2+x12>0\frac{3}{x^2 + x - 12} > 0, begin by factoring the denominator to yield 3(x+4)(x3)>0\frac{3}{(x + 4)(x - 3)} > 0. Determine the zero partition numbers by checking where the quotient is zero or undefined. Because the numerator is the constant 33, the quotient cannot be zero. The quotient is undefined when the denominator is zero, setting (x+4)(x3)=0(x + 4)(x - 3) = 0 gives x=4x = -4 and x=3x = 3. Use x=4x = -4 and x=3x = 3 as the zero partition numbers to separate the number line into intervals: (,4)(-\infty, -4), (4,3)(-4, 3), and (3,)(3, \infty). Testing points in each region shows the quotient is positive in the intervals (,4)(-\infty, -4) and (3,)(3, \infty). Because the inequality is strictly greater than 00, the endpoints are excluded. The complete solution written in interval notation is (,4)(3,)(-\infty, -4) \cup (3, \infty).

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Updated 2026-05-26

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