You have made an error in your second line, where you apply the product rule within the parentheses...you want a sum not a difference.
does this look right? https://www.dropbox.com/s/j7uatrtkdu...2022.41.07.jpg
if not..where did i mess up? and why does my ti-nspire cas give Undef as the answer?
how about now???
Yes, this looks right...I recommend writing the tangent line in slope-intercept form however.