A question about quadratic equations?

Question

I hope some1 on here is really, really smart.

I totally fell asleep in class and I'm totally confused on what we are supposed to do concerning quadratics. These are my following questions:
*How on earth do you find the axis of symmetry on a calculator(I've got one of them fancy TI ones from school)??
*what is the vertex of a parable(pronounced parabla i think)?
*number one says this: y= 2x^2 + 12x-11

I want to at least be able to solve number one!! I usually don't do this(ask a homework question on Yahoo Answers), but I am desperate! I'm not the type to fall asleep in class. Today was a bad day. Can anyone help me??

Answer 1

All Right, to find the axis of symetry, all you do is look at the vertex. The vertex is the lowest or highest point on a graph.

Lets say this is the parabola V. The vertex would be that bend at teh bottom

Then from here all you have to do to find the axis of symetry is find the x value of the vertex. Lets say the vertex is (3, 6) so the axis of symetry would be where x=3

hope that helps.

To graph the vertex:

1. Y=
1. Y1= 2x^2 + 12x -11
3. Trace
4. 2nd, Trace
5. Minimum
6. push enter on left side of the vertex then on the right, and it will tell you where the vertex is.

Answer 2

One equation for the parabola (puh -rab oh- luh) is:
y= ax^2 + bx + c
Your equation is y = 2x^2 +12X - 11
Do you see that for your equation, a =2, b = 12, and c = -11

The axis of symmetry is x = -b/2a = -12/(2*2) = -3
The vertex lies an the axis of symmetry so plug in x= -3 into original equation and get y = 2(-3)^2 +12(-3) - 11 = 18-36-11
= -29, so the vertex is at (-3,-29).

Answer 3

Input your equation into Y1 and make sure your stat plots are off and your zoom is set to standard

If its a positive equation(like number one), then you go to [2nd] [Calculate] Minimum(because its the lowest part of the curve)

If its a negative equation do the same thing except calculate Maximum....

make sure your bounds(it will ask you for bounds once you choose to calculate minimum or maximum) are wide enough include the highest or lowest part of the graph

The coordinates will be your vertex and your axis of symmetry is the X part of the vertex