Using the TI83 Calculator

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Using the TI-83 Calculator

• Lesson 5
• Linear Equations in
• Slope-Intercept Form

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Introduction

• The TI-83 calculator is a powerful tool for
  writing linear equations in slope-intercept form.
• By punching only a few buttons and entering a few
  pieces of information, the TI-83 can instantly
  generate a linear equation in slope-intercept
  form.

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Getting Started

• Two points are all you need to write an equation
  in slope-intercept form.
• By entering these two points, your calculator
  finds both the slope between these two points and
  the y-intercept of the line that connects these
  two points.

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Step 1 The STAT Button

• Begin by hitting the STAT key. This key is
  located to the left of the arrow keys, below the
  DEL key.
• After hitting STAT, the following screen will
  appear

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Step 2 The STAT Edit Screen

• From the STAT Menu screen, hit ENTER. This will
  take you to the STAT Edit screen.
• The STAT Edit screen is the screen where you will
  enter the two points into the calculator.
• The following screen is the STAT Edit screen

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Clearing Lists

• If your calculators screen was not like the
  sample screen, you need to clear the lists
  labeled L1 and L2.
• To clear the lists, use the arrow keys to
  highlight L1. Hit CLEAR on your calculator, then
  hit ENTER.
• Do the same to clear L2.

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Step 3 Entering the Points

• From the STAT Edit screen, you will enter the two
  given points to find the slope and y-intercept.
• On this screen, the x-value from each point will
  be entered into the L1 list, and the
  corresponding y-value will be entered into the L2
  list.

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Step 3 Continued

• For example, enter the following two points into
  L1 and L2
• (-2,4) and (3,-6)
• After entering the points, your screen should
  look like the following

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Step 4 The STAT Button Again

• Once the two points have been entered into lists
  L1 and L2, hit the STAT key again.

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Step 5 The CALC Functions

• From the STAT Menu screen, use the blue arrow
  keys to move the cursor over to highlight the
  CALC Menu.
• The following menu should be on your screen

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Step 5 LinReg (ax b)

• The fourth function on the CALC Menu is
  LinReg(axb), the linear regression function.
• From this screen, hit the number 4 key on your
  keypad.
• The following screen will appear

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Step 6 ENTER

• By hitting ENTER on this screen, the TI-83 will
  take the two points entered in L1 and L2 and
  calculate the slope and y-intercept of the line
  that connects those two points.
• For our example, the following screen will be the
  solution to our problem

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Step 7 Writing the Equation

• At this point, the TI-83 has given you all the
  information you need to write your equation.
• Note that your screen has the equation written as
  yaxb , with a and b below.
• In the normal slope-intercept form (ymxb), the
  slope of the equation is m.
• The TI-83 labels the slope as a.

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A Note about Slope

• Remember that slope needs to be written as an
  improper fraction.
• In the case that a is a decimal, retype the
  decimal answer on the TI-83 and use the FRAC
  function to get your slope in improper fraction
  form. (The same steps may be used for the
  y-intercept, b.)

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Solution to Example

• From the information on the calculator, you can
  now write the equation for the example of the
  (-2,4) and (3,-6)
• Y-2X0
• Rewritten as
• Y-2X

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Steps to Remember for Two Points

• STAT
• ENTER
• L1 x-values
• L2 y-values
• STAT
• CALC
• 4
• ENTER

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Further Examples

• For further practice, try writing equations for
  each of the following pairs of points
• 1. (0,-3) and (2, 7)
• 2. (12,9) and (-4,-7)
• 3. (-10,3) and (5,3)
• 4. (4,12) and (4,9)

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Solutions to Further Examples

• The following equations result from each pair of
  points
• Y5X-3
• YX-3
• Y3
• ERROR DOMAIN

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ERROR DOMAIN

• Why do you think that Example 4 resulted in an
  error?
• Look back at the two points used in Example
  4what do you notice?
• You should notice that the x-value is the same in
  both points.
• When the x-value is repeated, the graph of the
  line is vertical.

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ERROR DOMAIN Continued

• Anytime your TI-83 gives you ERROR DOMAIN, you
  should realize that the line you are graphing is
  a vertical line.
• Remember that the equation for a vertical line is
  X___.
• For Example 4, the equation would then be X4.

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Conclusion

• The more you use the TI-83 to write an equation
  in slope-intercept form, the easier it will
  become.
• To give you further practice using the TI-83
  to write linear equations, take the following
  quiz and write your answers on your own sheet of
  paper

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QUIZ

• (1,3) and (2,4)
• (-5,7) and (7,9)
• (1,6) and (1,9)
• (6,8) and (-3,8)
• (1,0) and (0,1)

• (6,18) and (3,9)
• (5,-3) and (5,-4)
• (-8,7) and (2,5)
• (3,8) and (5,11)
• (3,8) and (6,10)