How to determine whether a function is convex

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for example x’Ax / x’Bx A and B are Positive semidefinite matrix。

2

Study Convex Optimization – Boyd and Vandenberghe

Per Why isn't CVX accepting my model? READ THIS FIRST! you should be telling us, not asking us, whether a function id convex.

(x'*A*x)/(x'*B*x) where A and B` are positive semidefinite, is neither convex nor concave.

3

Thank you very much for answering this question. I have also proved this conclusion.