
David Gwyn J. answered 11/03/20
Highly Experienced Tutor (Oxbridge graduate and former tech CEO)
Vertex form of a parabola is y = a(x−h)2 + k with vertex at (h, k).
f(x) = x2
in which case, a = 1, h = 0, k = 0 and vertex must be at (0,0)
For translation 5 units up only, vertex will move to (0, 5)
=> h = 0, k = 5
Hence g(x) = x2 + 5