I understand that a black hole bends the fabric of space time to a point that no object can escape. I understand that light travels in a strait line along space time unless distorted by gravity. In Newton's Law of Universal Gravitation, the mass of both objects must be entered. If space time is being bent by gravity then light should follow that bend in space time. Why is that if a massless photon should not be effected by gravity in by Newton's equations? What am I missing?

I understand that a black hole bends the fabric of space time to a point that no object can escape. 

I understand that light travels in a straight line along spacetime unless distorted by gravity. If spacetime is being curved by gravity then light should follow that bend in spacetime.

In Newton's Law of Universal Gravitation, the mass of both objects must be entered, but photon has no mass, why should a massless photon be affected by gravity in by Newton's equations? What am I missing?