Solve a quadratic inequality and read its solution set

Enter the coefficients, choose the relation, and identify the intervals that satisfy it.

2 steps

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Finding the two boundary values is not enough when a problem asks for the set of values that satisfy an inequality. Use Inequality mode for this example:

x^{2} - 3 x + 2 > 0

Put the expression on the left and $0$ on the right before identifying the coefficients. In descending power order, they are $1$ , $- 3$ , and $2$ .

Solve it on the calculator

Below each step is the screen you should see after pressing.

Next to each step is the screen you should see after pressing.

Step 1

Open the mode picker. On the 991CW-style keypad, choose HOME → Inequality → degree 2; on other keypads, choose Inequality → degree 2. Select > above the coefficients and check that the screen reads $a x^{2} + b x + c > 0$ .

Press:
Step 2

Enter $1$ , $- 3$ , and $2$ in order. Press the equals key after each coefficient to advance; pressing it after $2$ solves the inequality. The display shows $x < 1$ and $2 < x$ on separate lines.

Press:

Read and check the result

The two displayed lines mean or, not and:

x < 1 or x > 2

Neither $1$ nor $2$ is included because the problem uses $>$ rather than $\geq$ . As a quick check, $x = 0$ and $x = 3$ each give $2 > 0$ on the left, while $x = \frac{3}{2}$ gives $- \frac{1}{4} < 0$ . If your problem uses another relation, change the selected sign before solving; these intervals are specific to the example.

The fx-991EX screen showing the solution x < 1 or x > 2 for x² − 3x + 2 > 0.

Solve a quadratic inequality on your fx-991EX calculator

Enter x² − 3x + 2 > 0 and read the solution intervals directly on the screen — it takes only a few seconds.

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Solve it on the calculator

Step 1

Step 2

Read and check the result

Solve a quadratic inequality on your fx-991EX calculator