请教以下微分方程组的求解问题

dingd

下面是用4阶龙格库塔得的结果，精度要高的多。

x y1 y2 y3 y4
0 13.0888626027927 0 20 -19.8094091074159
.1 13.7079005080915 11.6193644635588 18.3186742513779 -14.1216633219924
.2 15.2413667957476 18.1427859162973 17.1071198556988 -10.472294740897
.3 17.1458380047885 19.0014355954061 16.1479674285735 -9.08883486925347
.4 18.8544248090683 14.2993391566902 15.2144612395439 -9.92967344473984
.5 19.844105622683 4.80100497954744 14.0973926542481 -12.6890071155969
.6 19.6978481631122 -8.15939696933741 12.6299487596782 -16.8331678951509
.7 18.1541405221524 -22.8365164550568 10.7075247925527 -21.6640156894386
.8 15.1380489219684 -37.2811390426093 8.30014724173756 -26.4018647244596
.9 10.7701136657585 -49.5717115116983 5.45603222851198 -30.2780937120953
1 5.35202717829992 -58.0425762998741 2.29585672278697 -32.6264396273656
1.1 -.669204204541575 -61.4818061954345 -1.00157674109122 -32.9621315855897
1.2 -6.75435745650395 -59.2751419140305 -4.22057895261777 -31.0394658730281
1.3 -12.3360419892189 -51.4789374516877 -7.13419367644535 -26.880984088091
1.4 -16.8860929068778 -38.8134507089887 -9.53115495425049 -20.7747893910114
1.5 -19.97830358274 -22.5772781846928 -11.240980135337 -13.240320381293
1.6 -21.3390465205717 -4.49309873857963 -12.1542182212112 -4.96664860284778
1.7 -20.8797702256739 13.496949958271 -12.2354486139937 3.26937087589246
1.8 -18.7075126538984 29.4619566546753 -11.5274864960251 10.6953735544542
1.9 -15.1121830091354 41.7115828638517 -10.1462955488615 16.6352240381247
2 -10.5321230602689 48.9968294289083 -8.26721248005649 20.5893226641474
2.1 -5.50203899248626 50.65837766308 -6.10411976368502 22.2939419578161
2.2 -.58948867487782 46.7048868833759 -3.88404054738324 21.7525456459344
2.3 3.67253157395693 37.8119500974253 -1.82017335859093 19.2353709315542
2.4 6.84889353149098 25.2418337588769 -8.65694863189021E-02 15.2473243961348
2.5 8.65401770407302 10.6935364837247 1.20253927197232 10.468005486074
2.6 8.98578988434202 -3.89902214529341 2.00630723333833 5.67098203446672
2.7 7.93768556796251 -16.5967110607977 2.36212459604493 1.63190646826499
2.8 5.78766265075978 -25.6855107637123 2.38117451842225 -.963613412900842
2.9 2.9651422404565 -29.8800929986969 2.23522544355935 -1.60144630689466
3 5.21045880053084E-15 -28.4764772314602 2.13622763663515 -1.74664969987415E-15