Hi jgv115,

Calculus subforum is right.

This is the right answer, and I believe "from first principles" means use the definition of derivative as limit, and don't just use the shortcut of taking the exponent and moving it in front and subtracting one from the exponent.

This is just the line connecting the two points on a curve. MathWorld.

You can get the slope from your answer to part (a), now you can use point-slope equation.