SOLUTION: how do you figure out the height of the max/min when drawin a quadratic parobola??? for example (x+5)(x-3)

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: how do you figure out the height of the max/min when drawin a quadratic parobola??? for example (x+5)(x-3)      Log On


   

Question 350830: how do you figure out the height of the max/min when drawin a quadratic parobola???
for example (x+5)(x-3)
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Convert to vertex form, y=a%28x-h%29%5E2%2Bk.
The max or min occurs at the vertex, min if a%3E0, max if a%3C0.
Using your example,
y=%28x%2B5%29%28x-3%29
Use the FOIL method to expand,
y=x%5E2-3x%2B5x-15
y=x%5E2%2B2x-15
Complete the square to get into vertex form,
y=%28x%5E2%2B2x%2B1%29-15-1
highlight%28y=%28x%2B1%29%5E2-16%29
So the vertex occurs at (-1,-16).
Since a=1, the parabola opens upward and the vertex value is a minimum.
ymin=-16
.
.
.