1. The problem statement, all variables and given/known data Suppose two objects have energy fluxes, f and f + Δf, where Δf ≪ f. Derive an approximate expression for the magnitude difference Δm between these objects. Your expression should have Δm proportional to Δf. 2. Relevant equations Δm = m2 - m1 = 2.5 * log(f1/f2) 3. The attempt at a solution So the issue is that I'm not sure which of these solutions would be the better one to work with. However, I did make an approximation with the one as shown below and I'm not sure if it is quite accurate enough. Any assistance is greatly appreciated. Attempt 1: Δm = 2.5 * log(f / f+Δf) = 2.5 * [ log(f) - log (f + Δf)] or, Attempt 2: Δm = 2.5 * log(f+Δf / f) = 2.5 * log(1 + Δf/f) ≈ 2.5*Δf The second attempt seems more correct to me but I would feel more confident with a second opinion.