# Thread: Getting an equation from a parabola graph!!!!!!!

1. ## Getting an equation from a parabola graph!!!!!!!

i have this graph of a modified parabola, and i need to gets its equation, but i have no idea on how to do it, can some one show me how?

2. Originally Posted by Sneaky
i have this graph of a modified parabola, and i need to gets its equation, but i have no idea on how to do it, can some one show me how?
Start with the model $y = ax^2 + bx + c$. Now substitute the given data into this model to get a series of equations for a, b and c. Solve those equations simultaneously.

3. still dont get it, for the y=ax^2 +bx + c
i just get a point on the parabola line, (thats my x and y)
but what do i sub in as a b and c???

4. Originally Posted by Sneaky
still dont get it, for the y=ax^2 +bx + c
i just get a point on the parabola line, (thats my x and y)
but what do i sub in as a b and c???
Substitute the point (-2, 2) into y = ax^2 + bx + c. Get an equation.

Substitute the point (0, 1) into y = ax^2 + bx + c. Get an equation.

Substitute the point (1, -5/2) into y = ax^2 + bx + c. Get an equation.

Solve the three equations simultaneously for a, b and c.