The Quadratic Formula and Discriminant Analysis

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Last updated: 8/16/2025

Key Concepts:

  • Quadratic Formula: (x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}), used when factoring is difficult.
  • Discriminant \Delta Analysis: Determines the number of real solutions based on (b^2 - 4ac):
    • (\Delta > 0): Two real solutions
    • (\Delta = 0): One real solution
    • (\Delta < 0): No real solutions
  • Vieta's Formulas: The sum of the solutions to a quadratic equation can be expressed as (-\frac{b}{a}), the product of the solutions can be expressed as (\frac{c}{a}).

Skills Covered:

  • Using the quadratic formula
  • Applying the discriminant to determine the number of solutions
  • Applying Vieta's formulas to determine the sum or product of solutions

Example Problems:

  • Solve (2x^2 - 3x - 5 = 0) using the quadratic formula.
  • Determine how many real solutions exist for (3x^2 + 4x + 11 = 0).
  • Find the sum of solutions to the equation (2x^2 + 5x + 1 = 0).

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