Light Intensity: A & B, Distance D, Minimal Point?

[leprofece]

the intensity of iturninacion at any point is proportional to Ia intensity of light source and varies inversely as the square of the distance from the source. if two sources, A and B intensities, are at a distance D, at what point on the line that joins them, thee intensity of
Lighting will be minimal?. (Note: Supongase that the intensity at any point is the sum of the intensities due to both bulbs)

The same thinking I = ksenf/d²
and sin (h/d)
and d² = r²+h²

 

[MarkFL]

This problem is just a generalization of your other light source problem. I would work this problem first, and then use the formula you derive to answer the other question. I would probably use the substitution:

$$B=kA$$ where $0<k\in\mathbb{R}$