The functions y=C1e2x+C2xe2x form a two-parameter family of curves. Which of the following second-order differential equations is satisfied by every member of this family and is of the least possible order?
a) dx2d2y+4dxdy+4y=0
b) dx3d3y−4dx2d2y+4dxdy=0
c) dx2d2y−4dxdy+4y=0
d) dx2d2y−2dxdy+y=0