let n', m', i be Nat; :: thesis: for K being Field
for M' being Matrix of n',m',K
for p being FinSequence of K st len p = width M' holds
the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p))

let K be Field; :: thesis: for M' being Matrix of n',m',K
for p being FinSequence of K st len p = width M' holds
the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p))

let M' be Matrix of n',m',K; :: thesis: for p being FinSequence of K st len p = width M' holds
the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p))

let p be FinSequence of K; :: thesis: ( len p = width M' implies the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p)) )
assume A1: len p = width M' ; :: thesis: the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p))
set R = RLine M',i,((0. K) * p);
A2: ( Seg (len M') = dom M' & len M' = n' ) by FINSEQ_1:def 3, MATRIX_1:def 3;
per cases ( not i in dom M' or i in dom M' ) ;
suppose not i in dom M' ; :: thesis: the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p))
then ( RLine M',i,((0. K) * p) = M' & DelLine M',i = M' ) by A2, Th40, FINSEQ_3:113;
hence the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p)) ; :: thesis: verum
end;
suppose A3: i in dom M' ; :: thesis: the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p))
then A4: ( width M' = m' & width (RLine M',i,((0. K) * p)) = m' ) by A2, Th1, FINSEQ_1:4;
set KK = the carrier of K;
A5: len ((0. K) * p) = len p by MATRIXR1:16;
then ( Line (RLine M',i,((0. K) * p)),i = (0. K) * p & p is Element of (len p) -tuples_on the carrier of K ) by A1, A2, A3, FINSEQ_2:110, MATRIX11:28;
then Line (RLine M',i,((0. K) * p)),i = (len p) |-> (0. K) by FVSUM_1:71;
then A6: the_rank_of (RLine M',i,((0. K) * p)) = the_rank_of (DelLine (RLine M',i,((0. K) * p)),i) by A1, A4, Th90;
reconsider 0p = (0. K) * p as Element of the carrier of K * by FINSEQ_1:def 11;
RLine M',i,((0. K) * p) = Replace M',i,0p by A1, A5, MATRIX11:29;
then ( Replace (RLine M',i,((0. K) * p)),i,0p = Replace M',i,0p & i in NAT ) by FUNCT_7:36, ORDINAL1:def 13;
hence the_rank_of (DelLine M',i) = the_rank_of (RLine M',i,((0. K) * p)) by A6, COMPUT_1:7; :: thesis: verum
end;
end;