1. The problem statement, all variables and given/known data The problem I would like help with is 4.4 which is in the file 4.4.jpg. (The problem requires problem 4.2 which is why I included it as 4.2.jpg.) The solution is included however, I do not understand it since it is very brief and, I don't think I've covered this before. 2. Relevant equations V = IR R_(input,1) = ΔR/Δ11 (This equation makes no sense to me.) 3. The attempt at a solution I can see how I_1 = V_(input,1)/R_(input,1) = 60/R_(input,1) = 60/10 = 6 A but, the first equation with the deltas confuses me. Could someone please explain to me the logic behind that equation? Any help would be greatly appreciated!