F4 Maths...我有咩錯!

If the quadratic equation 4x^2-gx+15=0 has two distinct real roots which of the following are the possible values of g?

solution:
Because the quadratic equation 4x^2-gx+15=0 has two distinct real roots
∴ △﹥0
4x^2-gx+15﹥0
(-g)^2-4(4)(15)﹥0
g^2-240﹥0
g^2﹥240
g﹥±15.49...