▪ Solving Rational Inequalities

Learning Outcomes

  • Solve rational inequalities using boundary value method.

Solving Rational Inequalities using Boundary Value Method

Any inequality that can be put into one of the following forms

[latex]f(x)>0, f(x) \geq 0, f(x)<0, or f(x) \leq 0[/latex], where [latex]f[/latex] is a rational function

is called rational inequality.

How To: Solve Rational Inequalities

  1. Find restriction(s) of the given rational expression(s) in the inequality. The restriction(s) is(are) the boundary point(s).
  2. Rewrite the given rational inequality as an equation by replacing the inequality symbol with the equal sign.
  3. Solve the rational equation. The real solution(s) of the equation is(are) the boundary point(s).
  4. Plot the boundary point(s) from Step 1 & 3 on a number line.
    [latex]\Rightarrow[/latex] Use an open circle ALL restrictions.
    [latex]\Rightarrow[/latex] Use an open circle when the given inequality has [latex]<[/latex] or [latex]>[/latex]
    [latex]\Rightarrow[/latex] Use a closed circle when the given inequality has [latex]\leq[/latex] or [latex]\geq[/latex].
  5. Choose one number, which is called a test value, from each interval and test the intervals by evaluating the given inequality at that number.
    [latex]\Rightarrow[/latex] If the inequality is TRUE, then the interval is a solution of the inequality.
    [latex]\Rightarrow[/latex] If the inequality is FALSE, then the interval is not a solution of the inequality.
  6. Write the solution set (usually in interval notation), selecting the interval(s) from Step 5.

Example: Solving Rational Inequality using Boundary Value Method

Solve the rational inequality using boundary value method. Graph the solution set and write the solution in interval notation.

[latex]\frac{2x-1}{x+2} > 1[/latex]

Try It

Solve the rational inequality using boundary value method. Graph the solution set and write the solution in interval notation.

[latex]\frac{5x}{x-3} \leq 2[/latex]

Try It

Solve the rational inequality using boundary value method. Graph the solution set and write the solution in interval notation.

[latex]\frac{4x-5}{x+1} \geq 0[/latex]