A number of systems are specified below in terms of their input-output relationships. For each case, determine if the system is linear and/or time-invariant. y (t) = r (t)|+x (t) y (t) = tx (t) y (t) = e-tx (t) a. b. C. v(1) = y (t) = d. a (A) dA %3D y (t) = " r (A) d) t-1 e. t. v() -(+1) () 4a x (A) dX