Tyrus Lee inflection points on the function are where f is changing concavity. So where you see the graph changing from concave up to concave down, that’s an inflection point on f. Same logic for a change from concave down to concave up.
If you jump to around the 6 minute mark of this video, I explain in more detail: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-k22ReThVax0.html Hope that helps!
