A sign chart tracks whether the rational expression is positive or negative between consecutive critical values. Zeros of the numerator and values that make the denominator zero divide the real number line into intervals, and the sign remains consistent within each interval. Testing one point from each interval therefore identifies which regions satisfy the inequality.
A denominator zero is excluded from the domain because the rational expression is undefined there, so that value cannot belong to the solution set. A numerator zero may make the expression equal to zero and can be included when the inequality uses ≤ or ≥. This distinction determines whether boundary points receive closed or open endpoints.
Multiplication preserves an inequality’s direction only when the multiplier is positive. If the multiplier is negative, the direction reverses, and if its sign is unknown, the correct choice cannot be made immediately. Sign analysis avoids this uncertainty by examining intervals on which the relevant expression has a fixed sign.
List every real value that makes the numerator zero and every real value that makes the denominator zero. These values partition the number line into intervals where the expression can be tested. Numerator zeros are possible solution boundaries, whereas denominator zeros remain excluded because they represent domain restrictions.
First, identify domain restrictions and solve for the numerator’s zeros. Next, place all resulting critical values in order on a number line, test the rational expression on each interval, and select the intervals with the required sign. Finally, apply the original inequality symbol to decide whether eligible numerator zeros are included.
They can express whether a ratio of polynomial quantities stays above, below, or at a specified threshold. Solving the inequality identifies the ranges of a variable that meet that condition, while excluded denominator values mark discontinuities. The resulting intervals connect algebraic results with function behavior, including domain limits and asymptotic patterns.