Paper 3, Section I, A

Complex Methods
Part IB, 2017

By using the Laplace transform, show that the solution to

y4y+3y=te3t,y^{\prime \prime}-4 y^{\prime}+3 y=t e^{-3 t},

subject to the conditions y(0)=0y(0)=0 and y(0)=1y^{\prime}(0)=1, is given by

y(t)=3772e3t1732et+(5288+124t)e3ty(t)=\frac{37}{72} e^{3 t}-\frac{17}{32} e^{t}+\left(\frac{5}{288}+\frac{1}{24} t\right) e^{-3 t}

when t0t \geqslant 0.