# Thread: Find derivatives of functions

1. ## Find derivatives of functions

Alright, I have two questions. The first I think I have right, but I just want to make sure. The 2nd I have little or no clue on. Anyways, thanks in advance for the help.

Use the rules for derivatives to find the derivative of each function defined as follows

1.) y = 8e^5x

I came up with dy/dx = 40^5x by simply multiplying 8 by 5 eliminating the e and keeping the exponent. This appeared to be the process based on an example problem I looked at. Am I right...close...or way off?

2nd problem is from another section and I am lost

Find the derivative of each function defined as follows

2.) y = (2x^3 + 9x)^5

2. Originally Posted by Mathamateur
Alright, I have two questions. The first I think I have right, but I just want to make sure. The 2nd I have little or no clue on. Anyways, thanks in advance for the help.

Use the rules for derivatives to find the derivative of each function defined as follows

1.) y = 8e^5x

I came up with dy/dx = 40^5x by simply multiplying 8 by 5 eliminating the e and keeping the exponent. This appeared to be the process based on an example problem I looked at. Am I right...close...or way off?
I think you mean,
y=8*e^(5x)
In that case,
y'=40*e^(5x)
You are correct!

2nd problem is from another section and I am lost

Find the derivative of each function defined as follows

2.) y = (2x^3 + 9x)^5
y=u^5
u=2x^3+9x

dy/du=5u^4
du/dx=6x^2+9
Thus,
dy/du*du/dx=dy/dx=(6x^2+9)(5u^4)
Substitute,
5(6x^2+9)(2x^3+9x)^4