Find the focus of the parabola y = –1/4(x + 3)2 + 2.

Question

Find the focus of the parabola

Answer 1

y=(-1/4)(x+3)^2 +2

has vertex = (-3,2)

the focus has the same x coordinate as the vertex,-3. focus is (-3, z)

another point on the parabola is (-1, 1)

z-2 = sqr(4 +(z-1)^2)

z^2 -4z +4= 4 +z^2-2z +1

z=-1/2

focus is (-3, -.5)