; A := diag(a,b,c,d): B:=matrix(4,4,[0,0,0,a,0,0,b,0,0,c,0,0,d,0,0,0]): D1 := matrix(2,2,[e,0,1,e]); Z := matrix(2,2,0); G :=matrix(2,2,[0,1,0,0]); C := blockmatrix(2,2,[D1,Z,G,D1]); Ainv := inverse(A); Binv := evalm(1/B); Cinv := evalm(C^(-1)); ; ; ; ; ; C_I4 := augment(C,diag(1,1,1,1)); rref(C_I4);