Two Bulbs: Max & Min Intensity

[leprofece]

the intensity of the iluminacibn is directly proportional to the source intensity and inversely proportional to the square of Ia distance to the source. If two light bulbs are 16 cm of distance and one intensity of them is 4 times greater than the other, on which point of the line including Ia combined strength of the two foci is minimal?.

Remenbering
That I = ksin (f)/d²

and sin (h/d)
and d²= r²+h²

How must I organize this?? I tried with two triangles but i did not get the answer
Answer is = to 16/(1+cubic root of 4) from the more intesity bulb

 

[MarkFL]

I would probably begin by orienting a coordinate axis along the line between the two light sources and place the origin at one source. Then, for some point $x$ along the line between the sources, write the function that describes the intensity of light received, and then minimize that function.