find equation when given passing points

jordo6889 · #1 Nov 5, 2009, 09:12 AM

Find an equation of the form y=ax^2+bx+c whose graph passes through the points (-1,-4), (-3,-14) and (4,-14).

Perito · Nov 5, 2009, 09:31 AM

Quote:

Originally Posted by jordo6889

Find an equation of the form y=ax^2+bx+c whose graph passes through the points (-1,-4), (-3,-14) and (4,-14).

$y=ax^2 + bx + c$

Substituting point #1:

$-4 = a(-1)^2 + b(-1) + c$

Substituting point #2

$-14 = a(-3)^2 + b(-3) + c$

Substituting point #3

$-14 = a(4)^2 + b(4) + c$

If I did everything correctly, you now have three independent equations, and three unknowns. Solve the set of simultaneous equations for a, b, and c.