Holt McDougal Algebra 2

2-6 The Quadratic Formula

Warm UpWrite each function in standard form.

Evaluate b2 – 4ac for the given values of the valuables.

1. f(x) = (x – 4)2 + 3 2. g(x) = 2(x + 6)2 – 11

4. a = 1, b = 3, c = –33. a = 2, b = 7, c = 5

Holt McDougal Algebra 2

2-6 The Quadratic Formula

Solve quadratic equations using the Quadratic Formula.

Classify roots using the discriminant.

Objectives

Vocabulary

discriminant

Holt McDougal Algebra 2

2-6 The Quadratic Formula

You can use the Quadratic Formula to solve any quadratic equation that is written in standard form, including equations with real solutions or complex solutions. Remember that all quadratics are symmetric about the _____________________

Holt McDougal Algebra 2

2-6 The Quadratic Formula

Find the zeros using the Quadratic Formula.

Example 1: Quadratic Functions

f(x)= 2x2 – 16x + 27 f(x) = 4x2 + 3x + 2

Holt McDougal Algebra 2

2-6 The Quadratic Formula

The discriminant is part of the Quadratic Formula that you can use to determine the number of real roots of a quadratic equation.

Holt McDougal Algebra 2

2-6 The Quadratic Formula

Find the type and number of solutions for the equation.

Example 3: Analyzing Quadratic Equations by Using the Discriminant

x2 + 36 = 12x x2 + 40 = 12x x2 + 30 = 12x

Holt McDougal Algebra 2

2-6 The Quadratic Formula

The graph shows related functions. Notice that the number of real solutions for the equation can be changed by changing the value of the constant c.

Holt McDougal Algebra 2

2-6 The Quadratic Formula

An athlete on a track team throws a shot put. The height y of the shot put in feet t seconds after it is thrown is modeled by y = –16t2 + 24.6t + 6.5. The horizontal distance x in between the athlete and the shot put is modeled by x = 29.3t. To the nearest foot, how far does the shot put land from the athlete?

Example 4: Sports Application

Holt McDougal Algebra 2

2-6 The Quadratic FormulaProperties of Solving Quadratic Equations

Holt McDougal Algebra 2

2-6 The Quadratic FormulaProperties of Solving Quadratic Equations

Holt McDougal Algebra 2

2-6 The Quadratic Formula

No matter which method you use to solve a quadratic equation, you should get the same answer.

No matter which method you use to solve a quadratic equation, you should get the same answer.

Helpful Hint

HW pg 105 18-58e, 61-64