5 REM 7X7 MATRIX INVERSION
6 REM THIS MATRIX IS PROPOSED BY V. ALBILLO AS AN ILL CONDITIONED 
7 REM MATRIX, WHICH IS DIFFICULT TO CALCULATE; DETERMINANT IS -1
10 LET N=6
20 DATA 13,72,57,94,92,90,35,40,93,90,99,95,1,66,48,91,71,48,32 
21 DATA 93,67,7,93,29,2,24,24,7,41,84,44,40,27,82,49
22 DATA 3,72,6,33,34,97,4,43,82,66,43,29,83,61
30 DIM A(N,N), C(N,N), I(N,N)
40 MAT READ A
50 PRINT "ORIGINAL MATRIX:"
60 MAT PRINT A
70 PRINT
80 MAT C=INV(A)
90 IF DET=0 THEN 200
100 PRINT "DETERMINANT =";DET
110 PRINT
120 PRINT "INVERTED MATRIX:"
130 MAT PRINT C
140 PRINT
150 MAT I=C*A
160 PRINT "PROOF:"
170 MAT PRINT I
180 PRINT
190 STOP
200 PRINT "NO INVERSION POSSIBLE"
300 END

