缺4次项1元5次方程均可得“本源根”，含参数M，大家说说M是啥啊？

风花飘飘

X本源=
((sqrt(31)-3^(3/2))^(1/3)*(7*2^(4/3)*sqrt(3)*sqrt(31)-135*2^(1/3))*sqrt((sqrt(31)-3^(3/2))^(2/3)*(2^(1/3)*3^(3/2)*sqrt(31)-29*2^(1/3))+(sqrt(31)-3^(3/2))^(1/3)*(2^(2/3)*3^(3/2)-2^(2/3)*sqrt(31))+4*3^(3/2)*sqrt(31)-116)*M+(29*2^(2/3)*3^(3/2)*sqrt(31)-839*2^(2/3))*M+(sqrt(31)-3^(3/2))^(2/3)*(839-29*3^(3/2)*sqrt(31))*M)/((sqrt(31)-3^(3/2))^(1/3)*(261*2^(4/3)*sqrt(31)-839*2^(4/3)*sqrt(3)))