There is a SUPER easy reason why this is not the equation of the tangent LINE. It is something important though.
You are on the right track though. However, this is one of the problems with using rules of derivatives without knowing fully why we are using them.
If we are interested in finding the equation of the line tangent to the point , then we need to find some informatinon, most importantly what is the SLOPE of the line tangent to that point. But the slope of that line (if it containts that particular point), will be the same slope of that CURVE at the point yes?
Do you know what this actually refers to?
What you said was
"Find the equation of line tangent at point (1,5):
so will this be something like:
The reasonable interpretation of "this" is that it is your answer.