matlab解方程组matlab求解一个六元方程组,得出来的结果带回去不成立,matlab求解一个六元方程组,得出来的结果带回去不成立,symsxyx1y1x2y2[x,y,x1,y1,x2,y2]=solve('1+x1*x2+y2*x*x1+y2*x1*y=0','1

Question

matlab 解方程组 matlab求解一个六元方程组,得出来的结果带回去不成立,
matlab求解一个六元方程组,得出来的结果带回去不成立,
syms x y x_1 y_1 x_2 y_2
[x,y,x_1,y_1,x_2,y_2]=solve('1+x_1*x_2+y_2*x*x_1+y_2*x_1*y=0','1-x_2*y_1+y_2*x_1*x-y_2*y_1*y=0','x_2*x+0.5*y_2*x^2+y_2*x*y=0','x_2*y+0.5*y_2*y^2=0','x_1*x-y*y_1-5=0','x_1*x^2+2*x_1*x*y-y_1*y^2-200=0')
x =
40.0
0
y =
0.125
0.125
x_1 =
8.0
8.0
y_1 =
0
40.0
x_2 =
-0.125
-0.125
y_2 =
-0.4
-0.4

Answer 1

syms x y x_1 y_1 x_2 y_2
[x,x_1,x_2,y,y_1,y_2]=solve('1+x_1*x_2+y_2*x*x_1+y_2*x_1*y=0',...
'1-x_2*y_1+y_2*x_1*x-y_2*y_1*y=0',...
'x_2*x+0.5*y_2*x^2+y_2*x*y=0',...
'x_2*y+0.5*y_2*y^2=0','x_1*x-y*y_1-5=0',...
'x_1*x^2+2*x_1*x*y-y_1*y^2-200=0')
subs([1+x_1.*x_2+y_2.*x.*x_1+y_2.*x_1.*y,...
1-x_2.*y_1+y_2.*x_1.*x-y_2.*y_1.*y,...
x_2.*x+0.5.*y_2.*x.^2+y_2.*x.*y,...
x_2.*y+0.5.*y_2.*y.^2,x_1.*x-y.*y_1-5,...
x_1.*x.^2+2.*x_1.*x.*y-y_1.*y.^2-200])
发现两个解都对,并无错误.
注意matlab对解出的变量按字母先后顺序排序,不是随便排的,也不以变量的赋值顺序而改变,对这道题来说,就是按照[x,x_1,x_2,y,y_1,y_2]的顺序排的,不按这个顺序赋值就错了.