Question

Help? Range of y = −x2 + 4x − 21? I know that the x value for the vertex is -2. I am not sure how to find the range though?

Answer 1

range is all values that y takes. Since this parabola is opend down, this values are all y that are less than value of y at the vertex

Answer 2

Ok what I mean then is how can I find the y to the vertex? :L

Answer 3

\[y=a(x-h)^{2}+k\]
this is vertex form of this equation. (h,k) is the vertex. So put it in this form and you got it

Answer 4

so vertex is at (2,-17)