1. (16 pts) Indicate the kind of the equations below (each selection is worth 1 pt.):

    1. y(4) + sin(t)·y(3) + y = 1

      Order 4,   Linear,   Nonhomogeneous,   Variable coefficients. 

    2. t4y" + sin(y)·y' + y = 1

      Order 2,   Nonlinear,   Nonhomogeneous,   Variable coefficients. 

    3. y(4) + y(3) + y = sin(t)

      Order 4,   Linear,   Nonhomogeneous,   Constant coefficients. 

    4. y(4) + y(3) = y

      Order 4,   Linear,   Homogeneous,   Constant coefficients.