通常,系数未知的六次多项式的根不能以代数形式找到。除非你运气好,否则至少不会。运气和数学似乎对你不利吗?毕竟,这并不是随机的
Abel-Ruffini在很多年前证明了一般的五次多项式或更高
没有根式的代数解。所以我才说你需要特别的东西。幸运的是,你实际上伪装了一个三次多项式。我们知道如何解三次多项式的根。至少solve是这样的。我不会说我已经记住了这个公式,因为即使对我来说,它似乎也不值得。
相反,我们可以让MATLAB来完成繁重的工作。
符号【答案】d
A=A*w^6+b*w^4+c*w^2+d;
符号U
A_=subs(A,w^2,u)
A_u =
A *u^3 + b*u^2 + c*u + d
usol =解决(A_u,“maxdegree”3)
usol=
(((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) - b / (3 *) - (- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)
(- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) /(6 * ^ 2)) ^(1/3))——(3 ^ (1/2)* ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2
(2)(d//(2*a)a+b^3/(27*a^3)(b*c)/(27*a^3)(b*c)/(6*a^2(6*a^2)a^2(6*a^2)(3*a(3*a)甲-b^2/(3*a)2/(9*a第二)、2/(2/(9*a)b(3)(2/(3)a)b/(2/(2/(3)a)b(3(3)a)b(2/(2/(3)a)a)b(2/(2/(2/(2)(2/(2)(2)(2)(2)(2)(2)(3)a)a)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(3)a)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(3)a)a)a(二)(二)(二)(二)(二)(二)(三)(二)(三)(三/(27*a^3)(27*a^3)(27*a^a^3(27*a^3)a^3)(1/2)b^3(27*a^3(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^a^3)(1/2)3)(1/2)b(1/2)(1/2)b(1/2)b(1/2)b(7(27*a(27*a^3)(27*a^3)(3)b(27*a^3)(3)(3)(3)(3)(3)(27*a^3)b(27*a(27*a(27*a^3)(3)a(27)a(27(27)a(27)a(27)a(27)a(27)a(27)a(27)a(7)3)a(2)(3)(3)(3)(3)a(2)^(1/3)/2
wsol=[sqrt(usol);-sqrt(usol)]
wsol=
((((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) - b / (3 *) - (- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) ^ (1/2)
(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(c)(b)(b)(c)(b)(c)(c)(b)(c)(b)(c)(b)(c)(b(3)a)(a)(a)(3(a)(a)(b)(a)(a)(a)(b)(a)(a)(b)(b)(b)(b)(b)(b)(3)(3)a)(a)(a)(a)(a)(b)(b)(b)(b)(3)(3)a)(a)(a)(b)(b)(2)(2)(a)(a)(a)(2)(a)(a)(2)(a)(2)(a)(2)(a)(2)(a)(2)(a)(2)(2)(a)(a)(a)(a)(2)(a)(2)(a)(a)(a)(2)(2)(2)(2)(a)(a)(a)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(a)(a)(a)(a)(a)(a)(a)((二)(二)(二)(二)(二)(二)(三)(二)(三)(三/(27*a^3)(27*a^3)(27*a^a^3(27*a^3)a^3)(1/2)b^3(27*a^3(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^a^3)(1/2)3)(1/2)b(1/2)(1/2)b(1/2)b(1/2)b(7(27*a(27*a^3)(27*a^3)(3)b(27*a^3)(3)(3)(3)(3)(3)(27*a^3)b(27*a(27*a(27*a^3)(3)a(27)a(27(27)a(27)a(27)a(27)a(27)a(27)a(27)a(7)3)a(2)(3)(3)(3)(3)a(2)(1/3)/2)(1/2)
((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) + (3 ^ (1/2) * ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2) ^ (1/2)
-(b b*c)/(6*a^2)2+2(b^2/(9*a^2/(9*a^2+a^2+c/(3*a)3(a/(3*a)a/(3(a)(3)a)(3)3)3)3(1/2)b(1/2)b(1/2)(1/2)b(1/2)(1/2)b(1/2)b(1/2)b(1/2)b(1(2)b(2)b(2)b(2)b(2)(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)3)(2)(27(27(27(27(27)a)(1/3)(1/2)
((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) /(6 * ^ 2)) ^(1/3))——(3 ^ (1/2)* ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2) ^ (1/2)
((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) + (3 ^ (1/2) * ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2) ^ (1/2)
事实证明,solve足够聪明,可以隐式地计算出相同的结果。所以我可以这么做:
解决(,“maxdegree”6)
wsol=
((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) /(6 * ^ 2)) ^(1/3))——(3 ^ (1/2)* ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2) ^ (1/2)
((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) + (3 ^ (1/2) * ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2) ^ (1/2)
((((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) - b / (3 *) - (- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) ^ (1/2)
-(b b*c)/(6*a^2)2+2(b^2/(9*a^2/(9*a^2+a^2+c/(3*a)3(a/(3*a)a/(3(a)(3)a)(3)3)3)3(1/2)b(1/2)b(1/2)(1/2)b(1/2)(1/2)b(1/2)b(1/2)b(1/2)b(1(2)b(2)b(2)b(2)b(2)(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)(2)b(2)b(2)b(2)b(2)b(2)b(2)b(2)3)(2)(27(27(27(27(27)a)(1/3)(1/2)
(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(b)(c)(b)(b)(c)(b)(c)(c)(b)(c)(b)(c)(b)(c)(b(3)a)(a)(a)(3(a)(a)(b)(a)(a)(a)(b)(a)(a)(b)(b)(b)(b)(b)(b)(3)(3)a)(a)(a)(a)(a)(b)(b)(b)(b)(3)(3)a)(a)(a)(b)(b)(2)(2)(a)(a)(a)(2)(a)(a)(2)(a)(2)(a)(2)(a)(2)(a)(2)(a)(2)(2)(a)(a)(a)(a)(2)(a)(2)(a)(a)(a)(2)(2)(2)(2)(a)(a)(a)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(2)(a)(a)(a)(a)(a)(a)(a)((二)(二)(二)(二)(二)(二)(三)(二)(三)(三/(27*a^3)(27*a^3)(27*a^a^3(27*a^3)a^3)(1/2)b^3(27*a^3(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^3)(27*a^a^3)(1/2)3)(1/2)b(1/2)(1/2)b(1/2)b(1/2)b(7(27*a(27*a^3)(27*a^3)(3)b(27*a^3)(3)(3)(3)(3)(3)(27*a^3)b(27*a(27*a(27*a^3)(3)a(27)a(27(27)a(27)a(27)a(27)a(27)a(27)a(27)a(7)3)a(2)(3)(3)(3)(3)a(2)(1/3)/2)(1/2)
((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (2 * (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) + (3 ^ (1/2) * ((- b ^ 2 / (9 * ^ 2) + c / (3 *)) / (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (c / (3 *) - b ^ 2 / (9 * ^ 2)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) + (((d / (2 *) +b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3)) * 1) / 2 - b / (3 *) - (((d / (2 *) + b ^ 3 / (27 * ^ 3) - (b * c) / (6 * ^ 2)) ^ 2 + (- b ^ 2 / (9 * ^ 2) + c / (3 *)) ^ 3) ^ (1/2) - b ^ 3 / (27 * ^ 3) - d / (2 *) + (b * c) / (6 * ^ 2)) ^ (1/3) / 2) ^ (1/2)
我没有检查,但我猜这两组解决方案不必在同一个序列中。看起来它们不是。但是,经过充分的简化和适当的排序后金宝搏官方网站,它们应该是相同的,我不会这样做。