let n be Nat; :: thesis: for M1, M2 being Matrix of n,REAL st M1 is Negative holds
M2 is_less_than M2 - M1
let M1, M2 be Matrix of n,REAL; :: thesis: ( M1 is Negative implies M2 is_less_than M2 - M1 )
assume A1: M1 is Negative ; :: thesis: M2 is_less_than M2 - M1
A2: ( Indices M1 = [:(Seg n),(Seg n):] & Indices M2 = [:(Seg n),(Seg n):] ) by MATRIX_0:24;
A3: ( len M1 = len M2 & width M1 = width M2 ) by Lm3;
for i, j being Nat st [i,j] in Indices M2 holds
M2 * (i,j) < (M2 - M1) * (i,j)

proof

let i, j be Nat; :: thesis: ( [i,j] in Indices M2 implies M2 * (i,j) < (M2 - M1) * (i,j) )
assume A4: [i,j] in Indices M2 ; :: thesis: M2 * (i,j) < (M2 - M1) * (i,j)
then M1 * (i,j) < 0 by A1, A2;
then M2 * (i,j) < (M2 * (i,j)) - (M1 * (i,j)) by XREAL_1:46;
hence M2 * (i,j) < (M2 - M1) * (i,j) by A3, A4, Th3; :: thesis: verum

end;

hence M2 is_less_than M2 - M1 ; :: thesis: verum