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为了方便书写，记a = x[1] b = x[2] c = x[3]
则 a+b+c = 91/13, ab+bc+ca = 143/13, abc = -25/13
令 p = a+b+c, q = ab+bc+ca, r = abc
设
X = a^4*b+b^4*c+c^4*a
Y = a^4*c + b^4*a + c^4*b
则 (X+Y) 与 XY 都是对称多项式，可以表示成关于 p,q,r 的函数
经过计算，
XY = p^7*r-7*p^5*q*r+7*p^4*r^2+14*p^3*q^2*r-16*p^2*q*r^2-12*p*q^3*r+q^5+13*q^2*r^2 = 33756469/169
X + Y = p^3*q-p^2*r-3*p*q^2+5*q*r = 15866/13
解得 X = 7933/13 + 114*sqrt(2245)/13
≈ 1025.7294715123
则 a+b+c = 91/13, ab+bc+ca = 143/13, abc = -25/13
令 p = a+b+c, q = ab+bc+ca, r = abc
设
X = a^4*b+b^4*c+c^4*a
Y = a^4*c + b^4*a + c^4*b
则 (X+Y) 与 XY 都是对称多项式，可以表示成关于 p,q,r 的函数
经过计算，
XY = p^7*r-7*p^5*q*r+7*p^4*r^2+14*p^3*q^2*r-16*p^2*q*r^2-12*p*q^3*r+q^5+13*q^2*r^2 = 33756469/169
X + Y = p^3*q-p^2*r-3*p*q^2+5*q*r = 15866/13
解得 X = 7933/13 + 114*sqrt(2245)/13
≈ 1025.7294715123
