\[EmptySet] = A[1]*x^2 + A[2]*x*y + A[3]*y^2 + A[4]*x^3 + A[5]*x^2*y + A[6]*x*y^2 + A[7]*y^3 + A[8]*x^4 + A[9]*x^3*y + A[10]*x^2*y^2 + A[11]*x*y^3 + A[12]*y^4 \[Sigma]xx = D[\[EmptySet], y, y] \[Sigma]xy = -D[\[EmptySet], x, y] \[Sigma]yy = D[\[EmptySet], x, x] t1 = \[Sigma]xy /. y -> b t2 = \[Sigma]yy /. y -> b t3 = \[Sigma]xy /. y -> -b t4 = \[Sigma]yy /. y -> -b t5 = \[Sigma]xy /. x -> 0 t6 = \[Sigma]xx /. x -> 0 t7 = \[Sigma]xy /. x -> a t8 = \[Sigma]xx /. x -> a bc[1] = Coefficient[t1, x^2] bc[2] = Coefficient[t1, x] bc[3] = t1 /. x -> 0 bc[4] = Coefficient[t2, x^2] bc[5] = Coefficient[t2, x] bc[6] = t2 /. x -> 0 bc[7] = Coefficient[t3, x^2] bc[8] = Coefficient[t3, x] bc[9] = t3 /. x -> 0 bc[10] = Coefficient[t4, x^2] bc[11] = Coefficient[t4, x] bc[12] = t4 /. x -> 0 biharm = D[\[EmptySet], y, y, y, y] + 2*D[\[EmptySet], x, x, y, y] + D[\[EmptySet], x, x, x, x] f1 = Integrate[t7*y, {y, -b, b}] f2 = Integrate[t8, {y, -b, b}] f3 = Integrate[t7, {y, -b, b}] f4 = Integrate[t5, {y, -b, b}] f5 = Integrate[t6, {y, -b, b}] Solve[{bc[1] == 0, bc[2] == 0, bc[3] == 0, bc[4] == 0, bc[5] == 0, bc[6] == 0, bc[7] == 0, bc[8] == 0, bc[9] == 0, bc[10] == 0, bc[11] == 0, bc[12] == 0, biharm == 0, f1 == 100*12, f2 == 0, f3 == 100, f4 == 100, f5 == 0}, {A[1], A[2], A[3], A[4], A[5], A[6], A[7], A[8], A[9], A[10], A[11], A[12]}] 我的程式是这样打的 为什麽跑不出A[1]~A[12]的系数 谢谢!! --

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