(1 point) Given the system of equations (D + 8);: + Dzy = cos(t), m + (D + 7)y = tsin(t), (a) Write the system as a differential equation for x, in operator form, by filling the polynomial operator in D (on the left-hand-side of the equation) and the corresponding right-hand-side of the equation: Dx=D (Write your expression for the right-handside as a function of t only---that is, with no derivative operators.) (b) Note that we could equally well solve for y. Do this here, obtaining an equivalent differential equation for y. UPC] (Write your expression for the right-handside as a function of t only---that is, with no derivative operators.)