Question 1130868
f(x) = x^2 − 10x + 4
To complete the square for x^2 - 10x, since the linear term is -10, the constant term must be half of this, or -5:
(x - 5)^2 = x^2 - 10x + 25
25 = 21 + 4, so we need to subtract 21 to retain the original equation:
f(x) = (x - 5)^2 - 21
The standard form for a quadratic is y = a(x - h)^2 + k, where (h,k) is the vertex
Thus the vertex is (5,-21), and the axis of symmetry is x = 5