What is the domain and range of f-1(x) = -6 + or - squareroot of x+75/2

Answer 1

If f^-1(x) = (-6±√75)/2 then f(x) = 4x^2+24x-39 = 4(x+3)^2 - 75
so the domain is all reals
and the range is all reals >= -75

technically, f(x) = a(4(x+3)^2 - 75) so the range is y >= -75/a