Find the equation of the parabola y = ax² + bx + c that contains the points (1, -2), (2, 0), and (4, 22).
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Originally Posted by bearej50 Find the equation of the parabola y = ax² + bx + c that contains the points (1, -2), (2, 0), and (4, 22). Plug in the points and you'll get three equations. You can solve this system of equations in a number of ways. I recommend setting up a matrix. So let's write that as . We want to find x, hence: And you know how to calculate the inverse of a 3x3 matrix hopefully!
Last edited by Mush; May 10th 2009 at 12:46 PM.
I was taught a different way. Subtract the equations from one another. I got a = 13/5, b = -23/5, and c = 0. Is this right?
Originally Posted by bearej50 I was taught a different way. Subtract the equations from one another. I got a = 13/5, b = -23/5, and c = 0. Is this right? Check yourself if it is right. If it satisfies the original equations it's right. Unfortunately yours are not. I get a = 3 ,b = -7, c = 2, and that is correct.
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