Operation Manual

Chapter 17: Activities 294

Chapter 17:

Activities

The Quadratic Formula

Note: Each activity in this chapter assumes a default setting.

This example uses MathPrint™ mode for real answers and a classic format entry using division for non-

real (complex) results. You can also use the Polynomial Root Finder/Simultaneous Equation Solver

application to solve these types of problems with a quick set-up. This application comes pre-loaded on

your TI-84 Plus C and can be downloaded from education.ti.com.

Use the quadratic formula to solve the quadratic equations 2x

N 11x + 14 = 0 and 2x

N 6x + 5 = 0.

Graphing the Functions

Before you begin, look at the graphs of the functions to see the approximate locations of the solutions.

1. Press o

to display the Y= editor.

2. Press

2 „ ¡ ¹ 11 „ Ã 14 for Y1,

and then press Í.

3. Press

2 „ ¡ ¹ 6 „ Ã 5 for Y2.

4. Press q

and select 4:ZDecimal. The

graph of the functions displays.

Note: For quicker graphing, press y

.and set Detect Asymptotes OFF.

You can see that the graph of the first function,

N 11x + 14 = 0, crosses the x-axis, so it has a

real solution. The graph of the second function

does not cross the x-axis, so it has a complex

solution.