Exercises
[1TD]Prerequisites:[14W].Note:written exam, June 23th, 2012.
Let f be a \(C^ 1\) class function on \(β\), with \(f (0) β 0\). Prove that \(x β β\) exists such that the two vectors
\[ v = (x, f (x)) \quad , \quad w = (β f' (x), 1) \]are linearly dependent. (Note that the vector \(w\) is orthogonal to the tangent of the graph of \(f\).) Discuss the possibility that this condition is verified for every \(x β β\).
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