求解多元一次方程组a+b+c+d=9988a+4b+2c+d=64827a+9b+3c+d=19264a+16b+4c+

(1)a+b+c+d=998
(2)8a+4b+2c+d=648
(3)27a+9b+3c+d=192
(4)64a+16b+4c+d=18
(2)-(1)得
(5)7a+3b+c=-350
(3)-(1)得
(6)26a+8b+2c=-806
(4)-(1)得
(7)63a+15b+3c=-980
(6)-(5)*2得
(8)12a+2b=-106
(7)-(5)*3得
(9)42a+6b=70
(9)-(8)*3得
6a=388即a=194/3
把a代入(8)得b=-441
把a.b代入(5)得c=1561/3
把a.b.c代入(1)得d=854