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 60,53,61,65,50,37,64,49,78,67,67,24,10,50,31,52,59,60
21 DATA 32,19,33,18,51,50,82,35,27,21,10,18,30,36,38,12,11
22 DATA 6,18,14,33,13,33,10,61,57,63,72,51,45,66
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

