I have a question with respect to (iii) part of the question. I would like to know as to why we aren't interpolating for this and instead only adopting the trial and error method.
Hi Adithyan Good question. You could do interpolation. I think the issue with this question is that it requires you to be accurate to 2DP. Therefore, we have to show that the answer is r = 0.13 and not r = 0.12 or r = 0.14. This is why the solution looks at r = 0.125 and r = 0.135 and shows that the function switches from positive to negative somewhere between these values. Anna