Question

How do you graph parabolas?

Answer 1

I know I need a vertex and then 2 points on either side I just don't know how to find them

Answer 2

It sort of depends on what "form" the equation takes that determines which will be the easiest way to graph it I think.

Answer 3

For example, if they give you the equation in vertex form, y = a(x-h)^2 + k , you can begin by marking the vertex (h,k) , then use a to find two points on either side of the vertex.

Answer 4

What does the equation of your function look like?

Answer 5

y\[y =-\frac{ 7 }{ 4 }x ^{2}\]

Answer 6

So, this equation is in standard form: y = ax^2 + bx + c . Do you know how to use this form of the equation to find the vertex?

Answer 7

not really

Answer 8

If they give you the equation in standard form, you can find the x-coordinate of the vertex by using: x = -b/2a

Answer 9

So here you have y = -7/4 x^2 or y = -7/4x^2 + 0x + 0

Answer 10

So we need b and a. :) What is b and what is a for your function?

Answer 11

0

Answer 12

Yeah, b = 0 and a = -7/4 , so -b/2a = 0

Answer 13

okay I got that now how do we find the other coordinates?

Answer 14

So the x-coordinate of your vertex is 0. To find the y-coordinate you can just plug in the 0 for x in your original equation.

Answer 15

So y = -7/4 (0)^2 or 0 So (0,0) is the vertex. Then to find two other points

Answer 16

Use a. Start at the vertex, go one unit right and down a units. You can also start at the vertex and go one unit left and down a units.

Answer 17

I guess I should say, start at the vertex, go one unit right and vertically a units. So in this case one unit right and down 7/4.

Answer 18

Does that make sense?

Answer 19

So you would have a point at (1, -7/4) ... and where else?

Answer 20

So you have the vertex at (0,0), a point at (1, -7/4). And because the graph is symmetrical, where will you have another point?

Answer 21

If that didn't make sense please let me know and I will think of a better way to say it.