How to find the derivative of this function

**ImaCowOK** · September 10th 2010, 01:13 PM

$y = 6e^x$

Does the Power Rule apply? Or does $e^x$ stay the same? I tried with the Power Rule and it got confusing and messy.

**yeKciM** · September 10th 2010, 01:16 PM

Originally Posted by ImaCowOK

$y = 6e^x$

Does the Power Rule apply? Or does $e^x$ stay the same? I tried with the Power Rule and it got confusing and messy.

$(6e^x)' = 6e^x$

because when doing derivation you are doing derivation only of functions with "x"

can do it by chain rule

$(6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot e^x = 6e^x$

**ImaCowOK** · September 10th 2010, 01:32 PM

We haven't learned the chain rule, is there another way? If not, I'll just learn the chain rule.

**yeKciM** · September 10th 2010, 01:34 PM

Originally Posted by ImaCowOK

We haven't learned the chain rule, is there another way? If not, I'll just learn the chain rule.

you can look at it like this ...

$(6e^x)' = 6(e^x)' = 6e^x$

because you pull out the constant ... and now you just do derivation of the function with x

**mr fantastic** · September 10th 2010, 01:41 PM

Originally Posted by ImaCowOK

$y = 6e^x$

Does the Power Rule apply? Or does $e^x$ stay the same? I tried with the Power Rule and it got confusing and messy.

All you need are two things:

1. The derivative of e^x is e^x. (If you have not learned this then there is no point attempting questions that require knowing it).

2. If y = a f(x) then dy/dx = a f'(x).

**ImaCowOK** · September 10th 2010, 01:46 PM

Originally Posted by mr fantastic

If you have not learned this then there is no point attempting questions that require knowing it

Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.

**Plato** · September 10th 2010, 02:03 PM

Originally Posted by ImaCowOK

Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.

But surely you have a textbook or lecture notes.
Use them. Look up the topic even if you have not seen it in class.

**Revy** · September 10th 2010, 02:12 PM

Originally Posted by yeKciM

$(6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot e^x = 6e^x$

$(6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot (x)'e^x = 6e^x$
in case $x=-x$ answer would change to $-6e^{-x}$

**yeKciM** · September 10th 2010, 02:16 PM

Originally Posted by Revy

$(6e^x)' = 6' \cdot e^x + 6\cdot (e^x)' = 0\cdot e^x + 6 \cdot (x)'e^x = 6e^x$
in case $x=-x$ answer would change to $-6e^{-x}$

you should probably do :

$\displaystyle (Ae^{ax})' = ?$

$\displaystyle (Ae^{-ax})' = ?$

$\displaystyle (x^Ae^{ax})' = ?$

$\displaystyle (A^xe^{ax})' = ?$

Originally Posted by mr fantastic

Given the obvious background of the OP, the previous two replies are less than helpful. Post #5 is all that is required for the OP to understand at this point in time. Product rules etc. are not appropriate for this thread as it will just confuse the OP.

sorry about that ... del this post (#9) please

**mr fantastic** · September 10th 2010, 02:26 PM

Given the obvious background of the OP, the previous two replies are less than helpful. Post #5 is all that is required for the OP to understand at this point in time. Product rules etc. are not appropriate for this thread as it will just confuse the OP.

**mr fantastic** · September 10th 2010, 02:27 PM

Originally Posted by ImaCowOK

Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.

If that is true, then your problem is with the teacher and I would suggest that you discuss the matter with him/her.

**ImaCowOK** · September 10th 2010, 04:02 PM

Originally Posted by Plato

But surely you have a textbook or lecture notes.
Use them. Look up the topic even if you have not seen it in class.

Originally Posted by mr fantastic

If that is true, then your problem is with the teacher and I would suggest that you discuss the matter with him/her.

I do use the textbook as well as my notes. It's not as easy as that for someone who has never studied calculus before. I came here for help, not for a scolding. Is this not called "Math Help Forum"? If I have the wrong impression of what this site is for and my presence is bugging other users just say so and I'll leave. There's no need to be so insulting when you know nothing about the situation mr fantastic.

I've gotten all that I needed from this thread. Thanks.

**Defunkt** · September 10th 2010, 04:34 PM

Originally Posted by ImaCowOK

I do use the textbook as well as my notes. It's not as easy as that for someone who has never studied calculus before. I came here for help, not for a scolding. Is this not called "Math Help Forum"? If I have the wrong impression of what this site is for and my presence is bugging other users just say so and I'll leave. There's no need to be so insulting when you know nothing about the situation mr fantastic.

I've gotten all that I needed from this thread. Thanks.

You're being very defensive. I'm pretty sure they were both trying to help you. Try reading mr fantastic's comment tomorrow and you might see what he was trying to tell you - he didn't mean to insult / scold you at all.

**Plato** · September 10th 2010, 05:02 PM

I think you have a reading problem.
A Mathematics Help Forum is NOT a “Do it for me home-work” service.
You do understand that this is not a homework service?

**mr fantastic** · September 11th 2010, 03:46 AM

Originally Posted by ImaCowOK

I do use the textbook as well as my notes. It's not as easy as that for someone who has never studied calculus before. I came here for help, not for a scolding. Is this not called "Math Help Forum"? If I have the wrong impression of what this site is for and my presence is bugging other users just say so and I'll leave. There's no need to be so insulting when you know nothing about the situation mr fantastic.

I've gotten all that I needed from this thread. Thanks.

When someone says

Yep, that pretty much explains my class - homework problems on stuff we haven't been taught.

then I don't think it's unreasonable to say that

your problem is with the teacher and I would suggest that you discuss the matter with him/her

As for the "If" in my statement, it is not unknown for students to, unfairly, blame a teacher for their difficulties.

This thread is now closed.

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