\[Eta] = 1;
R = 0.05;
b = 3;
Num = If[b <= 3, b + 2, b - 1];
Subscript[\[Tau], s] = 0.5;
Subscript[R, 1] = b - (b - 1)*R;
Subscript[R, 2] = R;
Subscript[R, 3] = 1;
Subscript[R, 4] = R;
Subscript[R, 5] = Num + (Num - 1)*R;
Ux1[\[Xi]_] :=
Subscript[R, 1]*D[Subscript[U1, x1][\[Xi]], {\[Xi], 2}] +
2*(-\[Eta]*Subscript[\[Tau], s]);
Ux2[\[Xi]_] :=
Subscript[R, 2]*D[Subscript[U1, x2][\[Xi]], {\[Xi], 2}] +
2 (Subscript[U1, x3][\[Xi]] - Subscript[U1, x2][\[Xi]]) - (-\[Eta]*
Subscript[\[Tau], s]);
Ux3[\[Xi]_] :=
Subscript[R, 3]*D[Subscript[U1, x3][\[Xi]], {\[Xi], 2}] +
2 (Subscript[U1, x4][\[Xi]] - 2 Subscript[U1, x3][\[Xi]] +
Subscript[U1, x2][\[Xi]]);
Ux4[\[Xi]_] :=
Subscript[R, 4]*D[Subscript[U1, x4][\[Xi]], {\[Xi], 2}] +
2 (Subscript[U1, x5][\[Xi]] - 2 Subscript[U1, x4][\[Xi]] +
Subscript[U1, x3][\[Xi]]);
Ux5[\[Xi]_] :=
Subscript[R, 5]*D[Subscript[U1, x5][\[Xi]], {\[Xi], 2}] +
2 (Subscript[U1, x4][\[Xi]] - 2 Subscript[U1, x5][\[Xi]]);
(*Ux5[\[Xi]_]:=Subscript[R, 1]*D[Subscript[U1, \
x1][\[Xi]],{\[Xi],2}]+2*(-\[Eta]*Subscript[\[Tau], s]);*)
A = DSolve[{Ux1[\[Xi]] == 0, Ux2[\[Xi]] == 0, Ux3[\[Xi]] == 0,
Ux4[\[Xi]] == 0, Ux5[\[Xi]] == 0}, {Subscript[U1, x1][\[Xi]],
Subscript[U1, x2][\[Xi]], Subscript[U1, x3][\[Xi]],
Subscript[U1, x4][\[Xi]], Subscript[U1, x5][\[Xi]]}, \[Xi]];
Subscript[U1, b1] = Subscript[U1, x1][\[Xi]] /. A // Chop
上述微分方程解出来为：
{0.172414 \[Xi]^2 + C[1] + \[Xi] C[2]}
请问怎样可以省略C1常数项啊，很急，希望大神能帮我，万分感谢！

考虑 /. _C:>0