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Quadratic inequalities

This test develops methods for solving quadratic inequalities using roots and the sign of a parabola. Tasks cover selecting intervals, handling strict and non-strict boundaries and writing the solution in interval notation.

Questions: 10Estimated time: 17 minutes
Quadratic inequalities
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Sample questions

  1. Solve (x − (___))(x − (___)) > 0.
  2. Solve (x − (___))(x − (___)) < 0.
  3. Solve (x − (___))(x − (___)) ≤ 0.
  4. Solve x² < ___.
  5. Solve x² > ___.

Quadratic inequalities

Solve a quadratic inequality by analysing the sign of ax² + bx + c. First find its zeros, mark them on a number line and determine the sign on every resulting interval.

Parabola method

For a > 0, the parabola is above the x-axis outside two roots and below it between them; for a < 0, the signs reverse. The symbols ≤ and ≥ include roots, while < and > exclude them. With no real roots, the expression has the sign of a everywhere.

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