• November 2nd 2008, 09:03 AM
MonaMath
Hello, im doing this math homework in quadratics and i cant figure out this one

Determine the equation (in standard form) of the parabola that has a y-intercept of 3, and that passes through the points (1,9) and (-2,15)

this is supposed to be an inquiry question, i guess its relatevely easy but i dont know which one is the vertex and how do i use the y-intercept to help me solve it?
• November 2nd 2008, 09:20 AM
skeeter
Quote:

Determine the equation (in standard form) of the parabola that has a y-intercept of 3, and that passes through the points (1,9) and (-2,15)
you have three points ... (0,3) , (1,9) , and (-2,15)

using the form $y = ax^2 + bx + c$ , you can set up three equations ...

$a(0)^2 + b(0) + c = 3$

$a(1)^2 + b(1) + c = 9$

$a(-2)^2 + b(-2) + c = 15$

solve the system for the coefficients of the terms in the quadratic, a, b, and c.