Linearity
Since the system is linear the input, X[n], required to yield the output, Y[n]=u[n-1], is X[n]=u[n].
Time Invariance
Since the time shifting input, Xk[n]=d[n-k], yields the output, Yk[n]=(k+1)2 d[n-(k+1)], the system cannot be time invariant.
