Performing Computations to Derive the Quadratic Formula
Perform the following steps to derive the quadratic formula by
completing the square of the generalized quadratic equation.
1.
Clear all one-character variables in the
current folder.
@
2 ˆ
Choose
1:Clear a-z
confirm.
2.
On the Home screen, enter the generalized
quadratic equation:
3.
Subtract c from both sides of the equation.
@
2 ± | j
Note: This example uses the result of the
last answer to perform computations on the
TI-89 Titanium. This feature reduces
keystroking and chances for error.
4.
Divide both sides of the equation by the
leading coefficient
Note: Continue to use the last answer (2
±) as in step 3 in steps 4 through 9.
5.
Use the
expand( )
result of the last answer.
6.
Complete the square by adding
both sides of the equation.
7.
Factor the result using the
function.
Activities
and press ¸ to
2
.
ax
+bx+c=0
C
.
a
function to expand the
((b/a)/2)
factor( )
2
to
91