Question

The vertex of the graph of a function is (2, 0) and the y-intercept is (0, –4). Which of the following could be the equation of the function?

A) http://media.education2020.com/evresources/2003-18-01-00-00_files/i0220000.jpg

B)http://media.education2020.com/evresources/2003-18-01-00-00_files/i0220001.jpg

C)http://media.education2020.com/evresources/2003-18-01-00-00_files/i0220002.jpg

D)http://media.education2020.com/evresources/2003-18-01-00-00_files/i0220003.jpg

Answer 1

The vertex form of a quadratic function is
y=a(x−h)^2+k
where (h,k) is the vertex. Use your given vertex, and solve for a using the fact that you know the y-intercept.

Note that the vertex and any other point on the curve would be sufficient.