Example

Try It: Solving x+1x40\frac{x+1}{x-4} \leq 0

To find the values of xx that make the function R(x)=x+1x4R(x) = \frac{x+1}{x-4} less than or equal to 00, we solve the rational inequality x+1x40\frac{x+1}{x-4} \leq 0. First, determine the zero partition numbers by setting the numerator and denominator to zero: x+1=0    x=1x + 1 = 0 \implies x = -1 and x4=0    x=4x - 4 = 0 \implies x = 4. These partition numbers separate the number line into three intervals: (,1)(-\infty, -1), (1,4)(-1, 4), and (4,)(4, \infty). Testing values in each interval shows that the quotient is negative in the interval (1,4)(-1, 4). Because the inequality asks for values less than or equal to 00, the solution includes where the expression is negative or zero. The partition number x=4x = 4 must be excluded as it makes the denominator zero (undefined), while x=1x = -1 is included since it makes the numerator zero. Thus, written in interval notation, the solution is [1,4)[-1, 4).

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Updated 2026-05-25

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