9-6A Solving Quadratic Eq.’s
with Quadratic Formula
Algebra 1
Quadratic Formula

b  b 4ac
x
2a
2
Use the Quadratic Formula
 When you can’t factor a trinomial.
Identify the a, b & c
 ax 2+ bx + c = 0
Standard Form
 For example,
find b  4ac
2
2x + 7x – 15 = 0
 a=
 b=
 c=
Example 1
 2x 2 + 7x – 15 = 0
Example 2
Writing in Standard Form 1st
 3n2 - 8n = 2
Assignment

Example 3 -Finding the
x-intercepts of a graph
y  x  3x  8
2
Vertical Motion Models
 Object is dropped:
 Object is thrown:
h  16t 2  s
h  16t  vt  s
 h=height(ft)
 t=time in
motion(seconds
 s=initial height (ft)
 v=initial velocity
(ft/sec)
2
Example 4 – Modeling Vertical
Motion
 Six balloonists compete in the Field Target Event at a
hot-air balloon festival. Calculate the amount of time
it takes for the marker to hit the target when thrown
down from the given initial height (in feet) with the
given initial velocity (in feet per second);
s=200;v=-50