View Single Post
  #2   Spotlight this post!  
Unread 13-12-2004, 20:45
Kevin Sevcik's Avatar
Kevin Sevcik Kevin Sevcik is offline
(Insert witty comment here)
FRC #0057 (The Leopards)
Team Role: Mentor
 
Join Date: Jun 2001
Rookie Year: 1998
Location: Houston, Texas
Posts: 3,685
Kevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond reputeKevin Sevcik has a reputation beyond repute
Send a message via AIM to Kevin Sevcik Send a message via Yahoo to Kevin Sevcik
Re: can i have some help with quadratic equations

Well.... the standard to vertex thing is straight factoring. I'll demonstrate so you can see where those formulae come from:

We're trying to do this:
ax^2 + bx + c --> a(x-h)^2 + k

From here I'm just working with the left side:
(1) a(x^2 + b/a*x + c/a)

Now, we're looking for a perfect square. (x-h)^2 = x^2 - 2hx + h^2
so you match up the similar termsand get:
-2hx = b/a*x
h=-b/2a

plug this into (1) to get the squared term:

a(x^2 - 2hx + h^2 - h^2 + c/a)

note: the -2hx goes in cause we made it equivalent to b/a*x. the h^2 and -h^2 cancel out so you can add them in. you've got a perfect square in there now, so you factor it.
a((x - h)^2 - h^2 + c/a)
a(x - h)^2 + a(-h^2 + c/a)
a(x - h)^2 - ah^2 + c

now you just have that weird term out at the end. that's where k goes, so you set them equal to each other.
k = -a(h)^2 + c
k = -a(-b/2a)^2 + c
k = -b^2/4a + c

so there's your formula for h and k and how you get them.
h=-b/2a
k = -b^2/4a + c

This makes perfect sense to me, which undoubtedly means it's completely incomprehensible. so let me know what specifically isn't clear.
__________________
The difficult we do today; the impossible we do tomorrow. Miracles by appointment only.

Lone Star Regional Troubleshooter
Reply With Quote