2.9.3

Solving Quadratic Inequalities

Test yourself

Quadratic Inequalities

Find inequalities for x when x² > 9 and for x² < 9:

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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.
Illustrative background for x&sup2; < 9Illustrative background for x&sup2; < 9 ?? "content

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.

Jump to other topics

1Number

1.1Using Numbers

1.2Fractions, Decimals & Percentages

1.3Powers & Roots

1.4Accuracy

2Algebra

2.1Introduction to Algebra

2.2Manipulating Algebra

2.3Proofs & Functions

2.4Straight Line Graphs

2.5Common Graphs

2.6Transformations & Tangents

2.7Properties of Graphs

2.8Solving Equations

2.9Inequalities

2.10Sequences

3Ratio

4Geometry

4.1Introduction to Geometry

4.2Triangles & Quadrilaterals

4.3Transformations

4.4Circle Basics

4.5Circle Theorems

4.6Measurements & Units

4.7Calculating Area

4.8Triangle Formulae

4.93D Shapes

4.10Vectors

5Probability

6Statistics

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