
#1
Sep1806, 12:45 PM

P: 3

I have three points on a Y= ax^2 + bx + c graph (negative parabola). I don't know how to find the equation with this information. Tangent lines? Help.




#2
Sep1806, 12:51 PM

P: 2,048

Hi donlin. Welcome to PF!
Let's say one of the points is (x_{0}, y_{0}). What's ax_{0}^{2}+bx_{0}+c equal to? 



#3
Sep1806, 12:54 PM

HW Helper
P: 3,225

Your equation is a function of one variable, Y(x)=ax^2+bx+c. If a point (x0, y0) lies on the parabola, it must satisfy the equation f(x0) = y0. Since you have three points, after 'plugging' every one of them into the equation, you'll have three equations with three unknowns a, b and c, which are the coefficients you need.




#4
Sep1806, 01:15 PM

P: 3

Slopes of curves w/o equation?
I think I have the slope, by connecting point A to B and then rise over run, but I don't know how to get the rest of the equation. Basically, I have a point A and slope, but I don't have the coefficients or yintercept.




#5
Sep1806, 01:16 PM

P: 3





#6
Sep1806, 01:31 PM

P: 2,048





#7
Sep1806, 02:46 PM

Math
Emeritus
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Thanks
PF Gold
P: 38,885




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