Determine if the following systems are time- invariant, linear, causal, and/or memoryless? dy a) +6y(t) = 4x(t) dt dy b) +4ty(t) = 2x(t) dt c) y[n]+2y[n-1] = x[n+1] d) y(t)=sin(x(t)) dy e) + y² (t) = x(t) dt f) y[n+1]+4y[n] = 3x[n + 1] = x[n] Solve the following differential equations. Plot using Excel, MATLAB, or by hand for t=0, to t=6 (extra credit) a) dy |= dt +2y(t) =2x(t); x(t) = u(t), y(0) = -1 dy b) -2y(t) =2x(t); x(t) = u(t), y(0) = -1 dt