Answer: k = 16
Explanation:
The equation is written in the form:
y = ax^2 + bx + c
y = -x^2 - 6x + 7
y = a(x - h)^2 + k where (h, k) is the vertex
a = -1 (from the original equation)
h = -b/2a (this is the equation for the line of symmetry or the x-value of the vertex)
h = -(-6)/2(-1) = 6/-2 = -3
when x = -3, y = ?
y = -(-3)^2 - 6(-3) + 7
y = -(9) + 18 + 7
y = -9 + 18 + 7
y = 16
(-3, 16) is the vertex
Since k is the y-value of the vertex, k = 16
I'll just take it a step further and write the whole equation:
Substitute all the values we found
-1(x +3)^2 + 16
-(x + 3)^2 + 16