# Thread: Using Derivatives, find the equation of the tangent line.

1. ## Using Derivatives, find the equation of the tangent line.

Using Derivitives, find the equation of the tangent line at the given point.

x/(x-1) at the point (2,2).

So I don't know whether to immediately use the quotient rule to find f'(x), then plug in x = 2 for f'(x). Am I going about this wrong?

2. You are correct.Proceed.

3. Originally Posted by sa-ri-ga-ma
You are correct.Proceed.
f'(x)=-1/[(x-1)^2], so then f'(2)=-1?

is that correct, then what next?

4. What does the derivative tell you about the tangent line?

5. slope of the line its tangent to?
so y=mx+b right?

then f'(2)=-1 & f(x)=2, alright so here is where I'm stuck.

I haven't had math in a year.

6. Yes, use y = mx + c (or + b... haven't seen that, but it could work!)

You should be able to replace all but the c with values, and solve to find the value of c. What role does m play? ... so you have it here by another name. Likewise y. And you know the value of x, of course. So deduce c.