solve解非线性方程组

[xiaoxiong5227]

代码如下：
clear;clc
syms x1 x2 x3 x4 x5 x6 t2
y1=-221/14+6/35*x1+9/70*x3+3*x5*(1-t2)^2*t2;
y2=-69/14+6/35*x2+9/70*x4+3*x6*(1-t2)^2*t2;
y3=-233/14+9/70*x1+6/35*x3+3*x5*(1-t2)*t2^2;
y4=-7/2+9/70*x2+6/35*x4+3*x6*(1-t2)*t2^2;
y5=30*(1-t2)^3+3*(1-t2)^2*t2*x1+3*(1-t2)*t2^2*x3+90*t2^3-6233770349685199/140737488355328;
y6=-10*(1-t2)^3+3*(1-t2)^2*t2*x2+3*(1-t2)*t2^2*x4-30*t2^3-2480330921882157/281474976710656;
d=solve(y1,y2,y3,y4,y5,y6);
x1=vpa(d.x1,6)
x2=vpa(d.x2,6)
x3=vpa(d.x3,6)
x4=vpa(d.x4,6)
x5=vpa(d.x5,6)
x6=vpa(d.x6,6)
f=30*(1-t2)^3+3*(1-t2)^2*t2*x1+3*(1-t2)*t2^2*x3+90*t2^3-6233770349685199/140737488355328;
f=vpa(f,6)
t2=0:0.0001:1
plot(t2,subs(f))



为什么画出来的图形不是0 啊，是不是非线性方程组不能这样解啊？