I thought it was very clear, he test both before and after is his possible inflection point and finds a change in concavity, meaning it works at that x value. Then he plugs it back into the original function to find the exact point (not just x value) it changes. Where are you confused?
you solution for the inflection point was not really clear at all.
no really....not all of us use such calculators
I thought it was very clear, he test both before and after is his possible inflection point and finds a change in concavity, meaning it works at that x value. Then he plugs it back into the original function to find the exact point (not just x value) it changes. Where are you confused?