The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Quotient rule question

I just...

Posted from TSR Mobile
1384558613803.jpg35.7KB
Original post by The_Blade

What are you asking?
Reply 2
Avatar for The_Blade
The_Blade
OP
6
Can't do it

Posted from TSR Mobile
Original post by The_Blade


put dy/dx=0 in the usual way, noting that we cannot have x=0
Reply 4
Avatar for TenOfThem
TenOfThem
18
Original post by The_Blade


Put the x^-1 in the denominator so that you have x^7

Factorise the numerator and cancel appropriately

Put the fraction =0

Remember that if a fraction is 0 then it is the numerator that =0
Reply 5
Avatar for The_Blade
The_Blade
OP
6
Original post by TenOfThem
Put the x^-1 in the denominator so that you have x^7

Factorise the numerator and cancel appropriately

Put the fraction =0

Remember that if a fraction is 0 then it is the numerator that =0




Posted from TSR Mobile
1384609570476.jpg34.0KB
Reply 6
Avatar for TenOfThem
TenOfThem
18
Original post by The_Blade


the denominator is x^7

it would be x^(-7) if you have it in the numerator
Reply 7
Avatar for The_Blade
The_Blade
OP
6
Original post by TenOfThem
the denominator is x^7

it would be x^(-7) if you have it in the numerator


X^-1 ÷ X^6?

Posted from TSR Mobile
Reply 8
Avatar for TenOfThem
TenOfThem
18
Original post by The_Blade


yes - in the numerator

but x^6 x x^1 if in the denominator
Reply 9
Avatar for The_Blade
The_Blade
OP
6
Original post by TenOfThem
yes - in the numerator

but x^6 x x^1 if in the denominator


OK but I don't know how to go on from there. There answer is 1/3 e^-1

Posted from TSR Mobile
Reply 10
Avatar for The_Blade
The_Blade
OP
6
Original post by TenOfThem
yes - in the numerator

but x^6 x x^1 if in the denominator




Posted from TSR Mobile
1384814262951.jpg27.2KB
Original post by The_Blade


When you cancel x^3 you are left with x^4 in the denominator

Again though, the numerator = 0
Reply 12
Avatar for The_Blade
The_Blade
OP
6
Original post by TenOfThem
When you cancel x^3 you are left with x^4 in the denominator

Again though, the numerator = 0


Why is the numerator 0

Posted from TSR Mobile
Reply 13
Avatar for The_Blade
The_Blade
OP
6
Original post by TenOfThem
When you cancel x^3 you are left with x^4 in the denominator

Again though, the numerator = 0


I didn't get e^-1

Posted from TSR Mobile
1384816525827.jpg25.7KB
Reply 14
Avatar for Phichi
Phichi
11
You have done the last parts wrong. Personally I would divide the equation through by 3 to get:

13=lnx\frac{1}{3}=lnx

Then take e of both sides, which would give you:

e13=elnxe^{\frac{1}{3}}= e^{lnx}
e13=xe^{\frac{1}{3}}= x

Or:

3lnx≡lnx33lnx \equiv lnx^{3}

So,

e1=elnx3e^1 = e^{lnx^3}

e1=x3e^1 = x^3

x=e13x=e^{\frac{1}{3}}

Then sub the e13e^{\frac{1}{3}} back into the original equation
Reply 15
Avatar for The_Blade
The_Blade
OP
6
Original post by Phichi
You have done the last parts wrong. Personally I would divide the equation through by 3 to get:

13=lnx\frac{1}{3}=lnx

Then take e of both sides, which would give you:

e13=elnxe^{\frac{1}{3}}= e^{lnx}
e13=xe^{\frac{1}{3}}= x

Or:

3lnx≡lnx33lnx \equiv lnx^{3}

So,

e1=elnx3e^1 = e^{lnx^3}

e1=x3e^1 = x^3

x=e13x=e^{\frac{1}{3}}

Then sub the e13e^{\frac{1}{3}} back into the original equation


I don't see how that would get you 1/3 x e^-1 :frown:

Posted from TSR Mobile
Reply 16
Avatar for Phichi
Phichi
11
Original post by The_Blade
I don't see how that would get you 1/3 x e^-1 :frown:

Posted from TSR Mobile


We've found that:

x=e13x=e^{\frac{1}{3}}

Sub this into the original equation and find the value.

So:


13e1\frac{\frac{1}{3}}{e^1}

13e1=13e−1\frac{1}{3e^1} = \frac{1}{3}{e^{-1}}
(edited 10 years ago)
Reply 17
Avatar for The_Blade
The_Blade
OP
6
Original post by Phichi
We've found that:

x=e13x=e^{\frac{1}{3}}

Sub this into the original equation and find the value.

So:


13e1\frac{\frac{1}{3}}{e^1}

13e1=13e−1\frac{1}{3e^1} = \frac{1}{3}{e^{-1}}


I see now. Thanks dude

Posted from TSR Mobile

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you