Solving Quadratic Inequalities
Maths: Edexcel A Level Pure Maths, topic 2.3.3
Quadratic Inequalities
Find inequalities for x when x² > 9 and for x² < 9:
x² > 9
- Square root both sides.
- If x² is more than the answer, x must be smaller than the negative or larger than the positive.
x² < 9
- Square root both sides.
- If x² is less than the answer, x must be in between the two values.
- A useful check is to see if x = 0 satisfies the inequality.
- If it does x must be in between the two square roots.