Hi,
I have a test on quadratics tommorow and I need help!
Could someone explain to me how you go about determining a quadratic rule based on coordiantes of a parabola, or point me to a helpful site/tutorial?
Thanks,
22upon7
this might help
The Quadratic Formula: The Discriminant and Graphs
http://www.purplemath.com/modules/parabola.htm
Graphing Quadratic Functions: The Leading Coefficient / The Vertex
Each of those has a few pages worth of information.
If the leading coefficient is positive, it opens up.
If the leading coefficient is negative, it opens down.
If the discriminant is 0 you have one real root,
If the discriminant is positive you have two real roots,
If the discriminant is negative you have no real roots.
Complete the square to find the vertex.
This is a fairly typical system-of-equations word problem. You plug the x- and y-coordinates of the three points into the general formula for a quadratic. This gives you three equations in terms of the (unknown) coefficients "a", "b", and "c".
You solve the system of equations for the values of the coefficients, and thus for the required quadratic "rule".