Example

Try It: Solving x2x+40\frac{x-2}{x+4} \leq 0

To find the values of xx that make the function R(x)=x2x+4R(x) = \frac{x-2}{x+4} less than or equal to 00, we must solve the rational inequality x2x+40\frac{x-2}{x+4} \leq 0. First, find the zero partition numbers by setting the numerator and denominator to zero: x2=0    x=2x - 2 = 0 \implies x = 2 and x+4=0    x=4x + 4 = 0 \implies x = -4. These partition numbers divide the number line into three intervals: (,4)(-\infty, -4), (4,2)(-4, 2), and (2,)(2, \infty). Testing a value in each interval reveals that the quotient is negative in the interval (4,2)(-4, 2). Since the inequality requires the expression to be less than or equal to 00, the solution must include the values where the quotient is negative or zero. The partition number x=4x = -4 must be excluded because it makes the denominator zero (and thus the function undefined), while x=2x = 2 is included because it makes the numerator, and the entire function, equal to 00. Therefore, written in interval notation, the solution is (4,2](-4, 2].

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Updated 2026-05-26

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