value of a+b+c?

Question

If the graph of the equation y=ax²+bx+c passes through the points (0,2), (-6,-7), and (8,-14), what's the value of a+b+c?

Answer 1

How to solve this problem.   You are given three points on the parabola. For each point, substitute the x & y values of the ordered pair (coordinates) in for x and y, giving an equation involving unknown a, b, c.  you'll have a system of 3 linear equations for the three unknowns a,b,c.  Solve that system (I like to do it by using calculator's RREF command (under MATRIX menu(TI-83/84)). Or Cramer's rule is always fun, if doing it by hand.

 

Once you have solved for a, b & c, you just form their sum, and there's your answer!