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 86,69,53,33,18,10,87,70,65,63,55,20,25,73,44,53,63
21 DATA 67,45,44,49,32,27,50,84,36,12,33,28,41,39,64,51,45,33
22 DATA 11,20,13,17,19,33,15,88,73,55,35,21,18,90
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

