Specify the weak formulation for the differential equation \[ u''+\lambda \delta (x-1/2)u=f(x) \] subject to
boundary conditions \(u(0)=u(1)=0\).
Find all values of \(\lambda \) for which this differential equation with \(f(x)=0\) has a nontrivial
solution and verify that the corresponding solution is a weak solution.
Suppose \(\lambda \) is such that this differential equation with \(f(x)=0\) has only the trivial
solution. Find the solution with \(f(x)=1\).