matlab中計算四次方方程ax^4+bx+c=0的實數根.我是想計算ax^4+bx+c=0的x根,但是a、b、c是需要計算的,我想問下在matlab裡如何計算呢?我衹要那個正實數根,其他的都不要.在百度上看到你廻答類似的問題,但是不是很明白.

matlab中計算四次方方程a*x^4 b*x c=0的實數根.
我是想計算a*x^4 b*x c=0的x根,但是a、b、c是需要計算的,我想問下在matlab裡如何計算呢?我衹要那個正實數根,其他的都不要.在百度上看到你廻答類似的問題,但是不是很明白.

網友廻答：

匿名網友

syms a x b c
y = a*x^4 b*x c;
Y = solve(y, 'x')
結果如下：
ans =

1/12*6^(1/2)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2) 1/12*(-(6*12^(1/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 24*12^(2/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*c*a 72*b*6^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3)/(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2))^(1/2)
1/12*6^(1/2)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)-1/12*(-(6*12^(1/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 24*12^(2/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*c*a 72*b*6^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3)/(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2))^(1/2)
-1/12*6^(1/2)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2) 1/12*(-(6*12^(1/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 24*12^(2/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*c*a-72*b*6^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3)/(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2))^(1/2)
-1/12*6^(1/2)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)-1/12*(-(6*12^(1/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 24*12^(2/3)*(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2)*c*a-72*b*6^(1/2)*((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3)/(12^(1/3)*(((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(2/3) 4*c*12^(1/3)*a)/a/((9*b^2 (-768*c^3*a 81*b^4)^(1/2))*a)^(1/3))^(1/2))^(1/2)

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