An equation that hp prime can't solve

[yangyongkang]

Hello everyone, I am back. I recently encountered a system of equations, hp prime not only can not solve the exact solution, even the numerical solution can not be solved.

Code:

f:=(λ,μ)->(λ^4+λ^3*μ^2+λ^2*μ^2+λ^2*μ+λ^2+λ*μ^4+λ*μ^2+3*λ*μ*sqrt(λ^4+4*λ^3*μ+4*λ^3+2*λ^2​*μ^2+4*λ^2*μ+2*λ^2+4*λ*μ^3+4*λ*μ^2+4*λ*μ+4*λ+μ^4+4*μ^3+2*μ^2+4*μ+1)+μ^3+μ)/(λ^3*μ+λ*μ^3+λ*μ);fsolve([(∂(f(x,y),x))=0,(∂(f(x,y),y))=0],[x,y])

But when x=1, y=1 is indeed a set of solutions to the equation.
In fact we can test it

Code:

simplify((∂(f(x,y),x))|x=1,y=1);simplify((∂(f(x,y),y))|x=1,y=1)

PHP Code:

Is this not a BUG? 


Looking forward to the first firmware release in 2019, I hope CAS will be updated to 1.51-29