Find an equation of the tangent line to the curve at the point (-1, -1).
y = 5x^3 - 4x

Question

Find an equation of the tangent line to the curve at the point (-1, -1).
y = 5x^3 - 4x

zepdrix · Answer

$$\Large f(x)=5x^3-4x$$

I'm changing the notation to f(x), it'll make it easier to differentiate that from our tangent line.
So we want to find a line that is tangent to our curve at x=-1.
A line is of the form,$$\Large y=mx+b$$
The slope of this line $\Large m$ is given by $\Large f'(-1)$

zepdrix · Answer

Have you tried taking the derivative of your function yet? :)

anonymous · Answer

Thats probably the main issue. I'm not entirely sure about how to take the derivative

zepdrix · Answer

Since we have a nice polynomial function like this,
We can apply the `Power Rule for Derivatives`:$$\Large (x^n)' \quad=\quad nx^{n-1}$$
Have you learned about this yet?
Or are we supposed to solve this problem using the `Limit Definition of the Derivatve`?

anonymous · Answer

Yeah learned more about it a few days ago. Finished it.