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# Differentiating e^x

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### #1Pammy

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Posted 01 February 2007 - 04:01 PM

Differentiate (x+2) -

I keep getting -(x+2) -

But the answer is -(x+1) -

It might be quite easy, but I just can't seem to get the right answer.
*~* Pam xxx *~*
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

### #2will_789

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Posted 01 February 2007 - 04:39 PM

QUOTE(Pammy @ Feb 1 2007, 04:01 PM)
Differentiate (x+2) -

I keep getting -(x+2) -

But the answer is -(x+1) -

It might be quite easy, but I just can't seem to get the right answer.
*~* Pam xxx *~*

Theres a couple of ways you could tackle this: Product rule, or quotient rule.

Product rule you would get (x+2) . -e^-x + e^-x

Giving -(x+2)e^-x + e^-x

e^-x would be the common factor giving e^-x(-(x+2) + 1)

But now im lost lol...

I'll try and see what i could get from the quotient rule

### #3will_789

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Posted 01 February 2007 - 04:47 PM

QUOTE(will_789 @ Feb 1 2007, 04:39 PM)
QUOTE(Pammy @ Feb 1 2007, 04:01 PM)
Differentiate (x+2) -

I keep getting -(x+2) -

But the answer is -(x+1) -

It might be quite easy, but I just can't seem to get the right answer.
*~* Pam xxx *~*

Theres a couple of ways you could tackle this: Product rule, or quotient rule.

Product rule you would get (x+2) . -e^-x + e^-x

Giving -(x+2)e^-x + e^-x

e^-x would be the common factor giving e^-x(-(x+2) + 1)

But now im lost lol...

I'll try and see what i could get from the quotient rule

Got it.

Once you have -(x+2)e^-x + e^-x multiply out the brackets giving -xe^-x -2e^-x + e^-x

-2e^-x + e^-x = -e^-x

so leaves you with -xe^-x -e^-x

Take -e^-x out as a common factor, leaving you with -e^-x(x+1)

Hope thats right

### #4Pammy

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Posted 01 February 2007 - 05:02 PM

Thanx Will
You're a lifesaver, that question was cracking me up !!
Didn't even think to use the product rule, think I have frazzeled my brain with all my studying !!
*~* Pam xxx *~*
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

### #5will_789

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Posted 01 February 2007 - 05:03 PM

QUOTE(Pammy @ Feb 1 2007, 05:02 PM)
Thanx Will
You're a lifesaver, that question was cracking me up !!
Didn't even think to use the product rule, think I have frazzeled my brain with all my studying !!
*~* Pam xxx *~*

God, i have the seem feeling. Prelims are such a sack of s**t! Got maths tomorow, so im learning what i can lol. Hope that was the correct method for that question tho, but tbh, it was only the rearranging which was stupid, most of the marks are there for the differentiation and using the product rule

### #6Pammy

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Posted 01 February 2007 - 05:07 PM

O God tomorrow ??
That's crap !!!
Mine is Monday.
Good luck, and let me know how u get on !!
*~* Pam xxx *~*
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

### #7will_789

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Posted 01 February 2007 - 05:12 PM

QUOTE(Pammy @ Feb 1 2007, 05:07 PM)
O God tomorrow ??
That's crap !!!
Mine is Monday.
Good luck, and let me know how u get on !!
*~* Pam xxx *~*

### #8Pammy

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Posted 01 February 2007 - 05:15 PM

haha lol interesting ?? Sounds horrid !!
My chem isn't till the 16th so ive still got ages to study
Altho maths is on my birthday, so thts really mince
How are u gettin on with ur uni offers ??
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

### #9will_789

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Posted 01 February 2007 - 05:18 PM

QUOTE(Pammy @ Feb 1 2007, 05:15 PM)
haha lol interesting ?? Sounds horrid !!
My chem isn't till the 16th so ive still got ages to study
Altho maths is on my birthday, so thts really mince
How are u gettin on with ur uni offers ??

I got 6 uncles, yourself?

### #10Pammy

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Posted 01 February 2007 - 05:21 PM

woooo fab !!
What are u gonna go for ??
I've got 3 interviews (already done 2 of them)
An unconditional and 2 i havent heard from yet.
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

### #11will_789

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Posted 01 February 2007 - 05:24 PM

QUOTE(Pammy @ Feb 1 2007, 05:21 PM)
woooo fab !!
What are u gonna go for ??
I've got 3 interviews (already done 2 of them)
An unconditional and 2 i havent heard from yet.

I applied for the same course, 6 different uni's.
I'm off to do biomedical science! You still going for dentistry?

### #12Pammy

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Posted 01 February 2007 - 05:27 PM

What uni are u gonna go 2 ??
Yeah still goin 4 dentistry, that's what my interviews were for, wont hear if i get an offer till the end of march tho.
Had my Glasgow one (which is the one i want) last week and it seemed to go well, so fingers crossed !!
*~* Kiss me, beneath the milky twilight, lead me, out on the moonlit floor, lift your open hand, strike up the band and make the fireflies dance, silver moon sparkling, so kiss me *~*

### #13will_789

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Posted 01 February 2007 - 05:43 PM

QUOTE(Pammy @ Feb 1 2007, 05:27 PM)
What uni are u gonna go 2 ??
Yeah still goin 4 dentistry, that's what my interviews were for, wont hear if i get an offer till the end of march tho.
Had my Glasgow one (which is the one i want) last week and it seemed to go well, so fingers crossed !!

Unsure yet, either dundee or aberdeen

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