分岔测试中折线异常水平问题排查：代码修改后绘图异常

我正在用两个不同方程和参数测试分岔现象，第一部分代码运行正常，但复制代码仅修改一个方程和一个参数后，蓝线（r*x）却处于横轴位置，与预期不符。请求排查代码中导致该异常的原因：

正常运行的代码 #

assume(x>=0)
assume(x,"real")
rhigh = 1
rlow = 0.99
accuracy=0.000001
r=0.45
n=0
while abs(rhigh-rlow)>accuracy:
    r=(rhigh+rlow)/2
    n=n+1
    if len(solve((x^2)/(1+x^2)-r*x==0,x))==2:
        break
    elif len(solve((2*x^2)/(1+x^2)-r*x==0,x))==1:
        rhigh=r
    else:
        rlow=r
print(r)
print(n)
plot(r*x,(x,0,5))+plot((2*x^2)/(1+x^2)-r*x,(x,0,5),axes_labels=["x","values of x'"],color="cyan")

对应正常绘图 #

修改后异常的代码 #

assume(x>=0)
assume(x,"real")
rhigh = 1
rlow = 0.7
accuracy=0.000001
r=0.45
n=0
while abs(rhigh-rlow)>accuracy:
    r=(rhigh+rlow)/2
    n=n+1
    if len(solve((x^2)/(1+x^2)-r*x==0,x))==2:
        break
    elif len(solve((1.5*x^21+x^2)-r*x==0,x))==1:
        rhigh=r
    else:
        rlow=r
print(r)
print(n)
plot((r*x),(x,0,5))+plot(((1.5*x^21+x^2)-r*x),(x,0,5),axes_labels=["x","values of x'"],color="pink")

对应异常绘图 #

无法确定代码中哪部分导致蓝线处于横轴位置，请求协助排查。

内容的提问来源于stack exchange，提问作者Georgia Cox