Acc Algebra 1
Name: _______________________________
Unit 11: Lesson 5
Date: _________________ Period: _______
The Discriminant (9.6)
Essential Questions:
Why is the discriminant important?
Goal: Students will be able to use the discriminant to determine the number of solutions of a quadratic equation.
Key Ideas / Vocabulary:
 Discriminant:
the expression inside the radical of the quadratic formula _______________________
Purpose: the discriminant is used to find the number of _______________________ of a
quadratic function

If b 2  4ac is ______________________ then the equation has two
solutions.

If b 2  4ac is ______________________ then the equation has one
solution.

If b 2  4ac is ______________________ then the equation has no real
solutions.
Section 1: DISCRIMINANT… Find the value of the discriminant and use the value to tell the number of solutions.
1)
x 2  3x  4  0
YT 1) x 2  2 x  4  0
2)  x 2  2 x  1  0
YT 2)  3x 2  5x  1  0
3) 2 x 2  2 x  3  0
YT 3)  x 2  10 x  25  0
Section 2: MIXTURE OF QUADRATICS… Solve each question below.
4) Solve using Square Roots:
5) Solve by Graphing:
y  2 x 2  12 x  16
6) Solve by Quadratic Formula:
Homework:
16 y 2  80  0
4 x 2  11x  20
YT 4) Solve using Square Roots:
YT 5) Solve by Graphing:
f ( x)   x 2  6 x  1
YT 6) Solve by Quadratic Formula:
Unit 9: Quadratics Homework Packet # 71 - 80 All
Ticket Out / Lesson summary: How and why is the discriminant important?
1 2
x  7  4
3
x 2  3x  3  0