# Katie's question at Yahoo! Answers regarding a function and its given tangent line

#### MarkFL

Staff member
Here is the question:

If an equation of the tangent line to the curve y=f(x) at the point where a=2 is....?

y=4x-5, find f(2) and f'(2)

Please walk me through this question step by step.
I have posted a link there to this topic so the OP can see my work.

#### MarkFL

Consider the following diagram, showing the function $f(x)=x^2-1$ and its tangent line $y=4x-5$:
$$\displaystyle f'(2)=\frac{d}{dx}(4x-5)=4$$
$$\displaystyle f(2)=y(2)=4(2)-5=3$$