Paper 3, Section I, D

Variational Principles
Part IB, 2021

Find the function y(x)y(x) that gives a stationary value of the functional

I[y]=01(y2+yy+y+y2+yx2)dxI[y]=\int_{0}^{1}\left(y^{\prime 2}+y y^{\prime}+y^{\prime}+y^{2}+y x^{2}\right) d x

subject to the boundary conditions y(0)=1y(0)=-1 and y(1)=ee132y(1)=e-e^{-1}-\frac{3}{2}.