Question

The intensity of illumination at any point from a light source is proportional to the square of the reciprocal of the distance between the point and the light source. Two lights, one having an intensity six times that of the others, are 9 m apart. On the line between the two light sources, how far from the stronger light is the total illumination least?

Answer 1

Okay so \[
I = \frac k{r^2}
\]