Find the first two natural frequencies of a fixed-fixed uniform string of mass density \(ho\) per unit length stretched between \(x=0\) and \(x=l\) with an initial tension \(P\). Assume the deflection functions

\[\begin{aligned}& w_{1}(x)=x(l-x) \\& w_{2}(x)=x^{2}(l-x)^{2}\end{aligned}\]