vertex of parabola/graph of quadratic equation = (h,k)
h = -b/2a
k = 4ac - b²
4a
1) y = x² - 2x - 3
a = 1; b = -2; c= -3
h = -(-2)/ 2(1)
h = 2/2
h = 1
k = 4ac - b²
4a
k = 4(1)(-3) - (-2)²
4(1)
k = - 12 - 4
4
k = -16/4
k = - 4
Vertex form : a (x-h)² + k, substitute the values for h and k:
Vertex form: a(x-1)² - 4
2) -x² + 4x-1
a = -1; b = 4; c= -1
h = -(4)/2(-1)
h = -4/-2
h = 2
k = 4(-1)(-1) - (4)²
4(-1)
k = 4 - 16
-4
k = -12/-4
k = 3
Vertex form: Substitute the values for h and k:
Vertex form: - (x-2)² + 3
