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how do you find a quadratic formula from a list of ordered pairs?

I have a list of three ordered pairs of a quadratic function, and need to find the equation of the function. Any kind of help would be great. Thank you! the three ordered pairs are (20, 440); (30, 280); and (40, 200).

Public Comments

1. u must form 3 equations with 3 unknowns , then solve for the unknowns . let the function be y = ax^2 + bx + c solve for a , b , and c
2. use matrices. [x x^2 1] [a] [y] [x x^2 1] [b] = [y] [x x^2 1] [c] [y] so its a 3 by 3 multiplied by a 3 by 1, equals a 3 by 1. use inverse matrices to solve. each row is an ordered pair. the a,b,c matrix is the variable one. every other variable will be filled in with the numbers from the ordered pairs. ax^2+bx+c is your function.
3. Either use Lagrangian interpolation, or let the function be y = ax^2 + bx +c and plug in your three points to get three linear equations in the three unknowns a,b,c and solve them for a,b,c.