We use y{ }(nT)=-ay(nT)+bx(nT) to substitute for the derivative in y(nT) = ( frac{T}{2} [y^{ } (nT)+y^{ } (nT-T)]+y(nT-T) ) and thus obtain a difference equation for the equivalent discrete-time system. With y(n) = y(nT) and x(n) = x(nT), we obtain the result as of the following?

• A. ((1+ frac{aT}{2})Y(z)-(1- frac{aT}{2})y(n-1)= frac{bT}{2} [x(n)+x(n-1)] )
• B. ((1+ frac{aT}{n})Y(z)-(1- frac{aT}{n})y(n-1)= frac{bT}{n} [x(n)+x(n-1)] )
• C. ((1+ frac{aT}{2})Y(z)+(1- frac{aT}{2})y(n-1)= frac{bT}{2} (x(n)-x(n-1)) )
• D. ((1+ frac{aT}{2})Y(z)+(1- frac{aT}{2})y(n-1)= frac{bT}{2} (x(n)+x(n+1)) )