Determine whether each of the functions below is linear. Justify your answer. Recall that if you want to prove that a map is not linear, it suffices to find a counter-example. 1. A:R4->R4 defined by x1 x4
x2 -> x1
x3 x2
x4 x3
2. B:R2->R1 defined by x1 x2 -> x1+x2+1