Please use "^" to denote exponentiation: g(x) = 4 - x^2.
To find the critical point, differentiate g(x), set the result = to 0, and solve for x:
g '(x) = -2x = 0. Then x = 0 is the only critical value in this case.
The graph of g(x) is a vertical parabola opening down, and the horizontal tangent line is y = 4.
