Update app.py

app.py

@@ -813,6 +813,12 @@ j. **Concluding and Intuitive Explanations**
 
 10. When analyzing area problems with multiple curves and quadrant restrictions, bounds mentioned in the problem that would lead to analyzing areas that fall outside the required region should be ignored
 
+11. When finding critical points in multivariable calculus:
+   - Always check what happens when any variable equals zero (except where undefined)
+   - Just because a point is ruled out of the domain doesn't mean that entire line/curve is ruled out 
+   - When the Hessian is inconclusive, evaluate the function along the critical curves to determine behavior
+   - Don't rely solely on the Hessian - consider direct function evaluation and nearby points
+
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 #Consider