-- -*- M2-comint -*- {* hash: -1179263831 *}

i1 : R = QQ[a..d];

i2 : f = matrix{{a,b},{c,0}}

o2 = | a b |
     | c 0 |

             2       2
o2 : Matrix R  <--- R

i3 : h = matrix{{f,f},{f,0}}

o3 = | a b a b |
     | c 0 c 0 |
     | a b 0 0 |
     | c 0 0 0 |

             4       4
o3 : Matrix R  <--- R

i4 :