May 13, 2020 Thread starter #1 A awsomeman New member May 13, 2020 1 Let $f$ be differentiable from $(-\inf,0)$ to $(0,\inf)$ and let $f'(x)<0$ for all real numbers except 0 and $f'(0)=0$. Prove that f is strictly decreasing.

Let $f$ be differentiable from $(-\inf,0)$ to $(0,\inf)$ and let $f'(x)<0$ for all real numbers except 0 and $f'(0)=0$. Prove that f is strictly decreasing.

May 13, 2020 #2 J Joppy Well-known member MHB Math Helper Mar 17, 2016 256 You might want to begin by stating the definition of a decreasing function. Then consider some examples.

You might want to begin by stating the definition of a decreasing function. Then consider some examples.