but how can I solve with the chain rule with the y and u as I mentioned pls?
You forgot the dy/du part for the chain rule above; (dy/du)*(du/dx)=(dy/dx) Your du/dx is correct, just multiply it by dy/du and cancel and you should get the same answer
You forgot the dy/du part for the chain rule above; (dy/du)*(du/dx)=(dy/dx) Your du/dx is correct, just multiply it by dy/du and cancel and you should get the same answer