Question:How do I solve torsion equation with (non constant) Robin condition in a disc?

Question:How do I solve torsion equation with (non constant) Robin condition in a disc?

Maple 2021

$-\Delta u=1$ in $D$

$\frac{\partial u}{\partial\nu}+(x_1^2+1)u=0$ on $\partial D$

where $D=\{(x_1,x_2) : x_1^2+x_2^2<1\}$.

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