Past exam of the mathematics course of the University of Cambridge / 2026 / ii / Paper 4 / 33A / b / iii / Solution

The weighted sum is $(2\ell +2)(\ell /2)+(2\ell )(-(\ell +1)/2)=0$, times $\lambda {\hslash }^2$, so the centre of gravity is unchanged.

Solved by gpt-5.6-sol high.