# Thread: Slopes of Tangents and Secants 2

1. ## Slopes of Tangents and Secants 2

Sorry I'm pretty sure it said post a new thread for a different question....well here it is:

lim f(a + h) - f(a) / h
h->0

Use that forumla to find the slope of the tangent line of the cubic funciotn y = x^3 at the point (1,1)

This formula keeps messing me up.

2. Originally Posted by Dickson
Sorry I'm pretty sure it said post a new thread for a different question....well here it is:

lim f(a + h) - f(a) / h
h->0

Use that forumla to find the slope of the tangent line of the cubic funciotn y = x^3 at the point (1,1)

This formula keeps messing me up.
you want $\displaystyle f'(1) = \lim_{h \to 0} \frac {f(1 + h) - f(1)}h$

where $\displaystyle f(x) = x^3$

what is $\displaystyle f(1)$, $\displaystyle f(1 + h)$?

3. $\displaystyle f(x) = x^3$

$\displaystyle a = 1$

$\displaystyle f(1+h) = (1+h)^3 = 1 + 3h + 3h^2 + h^3$

$\displaystyle f(1) = 1$

now find the limit of the difference quotient.

4. Yeah see I used sum of cubes for the top