given a system t is time invariant,x1-x3 are inputs and y1-y3 are outputs x1[n]=δ[n], x2[n]=2δ[n-1], x3[n]=2δ[n-4] and y1[n]=2δ[n-1]+3δ[n-2], y2[n]=2δ[n-2], y3[n]=2δ[n+1],3δ[n+2] check if t could be linear