quadratic problem (f(x) = ax^2 + bx - 2, and two points)

[Guest]

f(x)=ax^2+bx-2
its graph crosses (-1,-3) and (1,3)
find the value of b.
I have tried to use the quatratic formular but it leads me nowhere.

 

[stapel]

The Quadratic Formula is used to solve "ax² + bx + c = 0", which you don't have, so I'm not sure how you might have "tried to use" that...?

You are given two points on the line. Plug them in. This will give you two equations in "a" and "b". Solve the resulting system of equations for the values of "a" and "b".

If you get stuck, please reply with a clear and complete listing of the steps and reasoning you have tried. Thank you.

Eliz.