Fitting a Parabola to Your Data

Using a Graphing Calculator:

Now let's use the same three points we found before on a graphing calculator.

Points A(-2,0), B(4,0), C(0,-8) must be entered as two columns of data:

Enter the Data Points:

1. Press the STAT 1 keys to get to the lists of data
2. Use the arrow buttons to move your cursor up to the top of column L₁, then press CLEAR ENTER
3. Do the same for data column L₂
4. Use the arrows to position the cursor in the first data cell under column L₁
5. Press (-) 2 ENTER, then 4 ENTER and 0 ENTER to enter all the X coordinates.
6. Use the arrows to position the cursor in the first data cell under column L₂
7. Press 0 ENTER, then 0 ENTER and (-) 8 ENTER to enter all the Y coordinates.
8. Press STAT, right-arrowto get to the CALC menu, then press 5 for the function QuadReg
9. Press ENTER and you should see

y = ax² + bx + c
a = 1
b = -2
c = -8

These coefficients correspond to the quadratic equation x² - 2x - 8 that we got when we did it algebraically!

Use your Back button to return to the algebraic fit page.