Lesson 4­6 The Quadratic Formula and the Discriminant with answers.notebook
January 27, 2015
Lesson 4­6 The Quadratic Formula and the Discriminant
Quadratic Formula ­ used to find the solutions to a quadratic equation in the form ax2 + bx + c = 0
http://youtu.be/mcIX_4w­nR0
Example 1
Solve x2 ­ 8x = 33 using the Quadratic Formula.
Example 2
Solve x2 ­ 34x + 289 = 0 using the Quadratic Formula.
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Lesson 4­6 The Quadratic Formula and the Discriminant with answers.notebook
January 27, 2015
Example 3
Solve x2 ­ 6x + 2 = 0 by using the Quadratic Formula.
Example 4
Solve x2 + 13 = 6x by using the Quadratic Formula.
Discriminant ­ used to determine the number and type of roots of quadratic equations
b2 ­ 4ac
If the discriminant is greater than 0 and a perfect square, there are 2 real, rational roots.
If the discriminant is greater than 0 and not a perfect square, there are 2 real, irrational roots.
If the discriminant equals 0, there is 1 real rational root.
If the discriminant is less than 0, there are 2 complex roots.
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Lesson 4­6 The Quadratic Formula and the Discriminant with answers.notebook
January 27, 2015
Example 5
Find the value of the discriminant for each quadratic equation. Then describe the number and type of roots for the equation.
a. x2 + 3x + 5 = 0
b. x2 ­ 11x + 10 = 0
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Lesson 4­6 The Quadratic Formula and the Discriminant with answers.notebook
January 27, 2015
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