# Find expressions for the quadratic functions

• January 31st 2009, 06:40 PM
question111
Find expressions for the quadratic functions
Find expressions for the quadratic functions whose graphs are shown:

http://img204.imageshack.us/img204/8...aticqv3.th.png
• January 31st 2009, 06:44 PM
Jhevon
Quote:

Originally Posted by question111
Find expressions for the quadratic functions whose graphs are shown:

http://img204.imageshack.us/img204/8...aticqv3.th.png

there are several ways to approach this. here's one

note that the vertex is on the x-axis, that is, we have a double root for the vertex

thus, our quadratic is of the form $y = a(x - 3)^2$

we are given that the point (4,2) is on the graph, we can use this to find $a$, by plugging in $x = 4$ and $y = 2$ into the form above

• January 31st 2009, 06:50 PM
Shyam
Quote:

Originally Posted by question111
Find expressions for the quadratic functions whose graphs are shown:

http://img204.imageshack.us/img204/8...aticqv3.th.png

Your image is so small that it is very hard to see the co-ordinate of vertex and a point in parabola. Please write these coordinates, then it will be solved.
• January 31st 2009, 06:51 PM
Jhevon
Quote:

Originally Posted by Shyam
Your image is so small that it is very hard to see the co-ordinate of vertex and a point in parabola. Please write these coordinates, then it will be solved.

if you click on the image, it takes you to a larger one
• February 1st 2009, 03:38 PM
question111
So a would be 2, and when I plug that in, I am finally getting a graph like it's shown in the book.

Thank you very much.
• February 1st 2009, 04:11 PM
Jhevon
Quote:

Originally Posted by question111
So a would be 2, and when I plug that in, I am finally getting a graph like it's shown in the book.

Thank you very much.

• January 24th 2010, 11:48 PM
lovegreen
and so what is your expression
(Thinking)
• January 24th 2010, 11:54 PM
Jhevon
Quote:

Originally Posted by lovegreen
(Thinking)

i do not understand your question. we found that a = 2. just plug that into the expression given in post #2 to get the quadratic
• January 25th 2010, 01:32 AM
lovegreen
Thanks!
I see it is y = 2(x squared) -12x + 18
• January 25th 2010, 04:43 AM
HallsofIvy
Quote:

Originally Posted by lovegreen
I see it is y = 2(x squared) -12x + 18

Why not just leave it as $y= 2(x- 3)^2$?