10 CLEAR :CLS 15 PRINT "PROGRAMA DE RESOLUCION DE SIST. DE ECS.DIFERENCIALES" 20 INPUT "X0";X,"Y0";Y,"Z0";Z,"H";H,"X";X1 23 PRINT "Y'=F(X,Y,Z)=";:INPUT F$:PRINT "Z'=G(X,Y,Z)=";:INPUT G$ 24 N=(X1-X)/H 25 FOR I=1 TO N 26 XI=X:YI=Y:ZI=Z 35 K1=VALF(F$):L1=VALF(G$):X=X+H:Y=Y+H*K1:Z=Z+H*L1 50 K2=VALF(F$):L2=VALF(G$) 60 Y=YI+H/2*(K1+K2):Z=ZI+H/2*(L1+L2) 70 NEXT I 80 PRINT "Y=";Y,"Z=";Z 90 GOTO 20