Algebra help please help as soon as you can

Find an equation in standard form for the parabola passing through the given points.
(-7, 220) (3, 0) (7, 80)

You have 6 known values - 3 x values and 3 y values. You also have the equation for a parabola,

Ax^2 + Bx + C = y

Which is really 3 equations,

Ax1^2 + Bx1 + C = y1
Ax2^2 + Bx2 + C = y2
Ax3^2 + Bx3 + C = y3

There you go, 3 equations and 3 unknowns. It's a linear system. Need more help? No problem. Here's how you solve a linear system with 3 variables:

http://www.sosmath.com/soe/SE3/SE3.html

Just linking because they do a better job explaining than I can here. Good luck to you!

The general equation for a parabola is given by:

y = ax² + bx + c

We need three independent equations to solve for "a," "b," and "c," and we can use the three points to get those three equations.

For point (-7,220):

220 = a(-7)² + b(-7) + c

49a -7b + c = 229 . . . . . . . . . . . . . . (1)

For point (3,0):

0 = a(3)² + b(3) + c

9a +3b + c = 0 . . . . . . . . . . . . . . (2)

For point (7,80):

80 = a(7)² + b(7) + c

49a +7b + c = 80 . . . . . . . . . . . . . (3)

Thus, our three equations are:
49a -7b + c = 220
9a +3b + c = 0
49a +7b + c = 80

a=3
b=-10
c=3

the equation becomes:

y=3x^2-10x+3