## Basic program for simultaneous equations

This program solves n equations with n unknowns.
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10 REM GAUSS ELIM
20 PRINT "WRITE EQN AS 2X + 3Y + 4Z = 9"
30 PRINT "ENTER GOING ACROSS. EG. 2 3 4 9"
40 PRINT
50 PRINT "THIS ALGORITHM OCCASSIONALLY FAILS BY /0."
60 PRINT
100 DIM A(15, 16), X(15)
110 INPUT "NO. OF EQUATIONS "; N
115 PRINT "TYPE COEFF."
120 FOR I = 1 TO N
130 FOR J = 1 TO N + 1
140 INPUT A(I, J)
150 NEXT J
155 PRINT "------------------"
160 NEXT I
169 PRINT
170 GOSUB 1000
180 FOR I = 1 TO N
200 PRINT "X("; I; ") = "; X(I)
210 NEXT
220 END
1000 FOR K = 1 TO N - 1
1010 JJ = K
1020 FOR I = K + 1 TO N
1030 QT = A(I, K) / A(K, K)
1040 FOR J = K + 1 TO N + 1
1050 A(I, J) = A(I, J) - QT * A(K, J)
1060 NEXT J
1070 NEXT I
1080 FOR I = K + 1 TO N
1090 A(I, K) = 0
1100 NEXT I
1110 NEXT K
1120 X(N) = A(N, N + 1) / A(N, N)
1130 FOR NX = 1 TO N - 1
1140 SUM = 0
1150 I = N - NX
1160 FOR J = I + 1 TO N
1170 SUM = SUM + A(I, J) * X(J)
1180 NEXT J
1190 X(I) = (A(I, N + 1) - SUM) / A(I, I)
1200 NEXT NX
1210 RETURN

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