Consider the first-order linear differential equation
y(t) + 5 (dy(t) / dt) = x(t)
Compute the zero-input response (general solution of the homogeneous equation) to find the system-specific part of the response (output) etc.
Compute the unit-step response, that is, the response when x1(t) = u(t), y(t)t=0 = 0. Call this response y1(t).