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**a**. Determine all critical points of the given system of equations.

**b.**Find the corresponding linear system near each critical point.

**c.**Find the eigenvalues of each linear system. What conclusions can you then draw about the nonlinear system?

**d.**Draw a phase portrait of the nonlinear system to confirm your conclusions, or to extend them in those cases where the linear system does not provide definite information about the nonlinear system.

$$

\left\{\begin{aligned}

&\frac{dx}{dt} = 1 - y\\

&\frac{dy}{dt} = x^2 - y^2

\end{aligned}\right.$$