quick differentiation question Watch

This discussion is closed.
zoidberg
Badges: 1
Rep:
?
#1
Report Thread starter 14 years ago
#1
probably easy:

diff. 3^(2x) w.r.t.x

thanks
0
Nylex
Badges: 10
Rep:
?
#2
Report 14 years ago
#2
(Original post by zoidberg)
probably easy:

diff. 3^(2x) w.r.t.x

thanks
y = 3^2x

ln y = ln 3^2x

ln y = 2xln 3

Implicit differentiation for LHS: 1/y dy/dx = 2ln 3

dy/dx = y.2ln 3

dy/dx = 2ln 3.3^2x
0
George-W-Duck
Badges: 2
Rep:
?
#3
Report 14 years ago
#3
(Original post by Nylex)
y = 3^2x

ln y = ln 3^2x

ln y = 2xln 3

Implicit differentiation for LHS: 1/y dy/dx = 2ln 3

dy/dx = y.2ln 3

dy/dx = 2ln 3.3^2x
So not that easy really...!
0
Ralfskini
Badges: 10
Rep:
?
#4
Report 14 years ago
#4
(Original post by zoidberg)
probably easy:

diff. 3^(2x) w.r.t.x

thanks

let y=3^2x.
lny=2xln3
dy.dx=3^2x.2ln3.
0
zoidberg
Badges: 1
Rep:
?
#5
Report Thread starter 14 years ago
#5
thanks
0
scottyoneill
Badges: 0
#6
Report 14 years ago
#6
can u not use the chain rule for that?
0
john !!
Badges: 14
Rep:
?
#7
Report 14 years ago
#7
I don't think you can because the index is a variable (contains x).
0
Nylex
Badges: 10
Rep:
?
#8
Report 14 years ago
#8
(Original post by mik1a)
I don't think you can because the index is a variable (contains x).
Yeah, that's right.
0
Leekey
Badges: 9
#9
Report 14 years ago
#9
This is the standard y=a^x thingy thats one the syllabus isn't it?!? I seem to have a vague memory of being told that it was quite important.... :confused:
Nylex
Badges: 10
Rep:
?
#10
Report 14 years ago
#10
(Original post by Leekey)
This is the standard y=a^x thingy thats one the syllabus isn't it?!?
Yep.
0
JamesF
Badges: 1
Rep:
?
#11
Report 14 years ago
#11
You dont actually need to do quite that,
3^(2x) = 9^x = e^(xln9)

dy/dx = ln9 * 9x = 2ln3 * 3^(2x)
0
Leekey
Badges: 9
#12
Report 14 years ago
#12
(Original post by JamesF)
You dont actually need to do quite that,
3^(2x) = 9^x = e^(xln9)

dy/dx = ln9 * 9x = 2ln3 * 3^(2x)
I still prefer taking logs and then using the product rule.
X
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of the West of England, Bristol
    Undergraduate Open Afternoon - Frenchay Campus Undergraduate
    Wed, 23 Jan '19
  • University of East London
    Postgraduate Open Evening Postgraduate
    Wed, 23 Jan '19
  • University of Gloucestershire
    School of Education Open Day Postgraduate
    Wed, 23 Jan '19

Brexit: Given the chance now, would you vote leave or remain?

Remain (1629)
78.92%
Leave (435)
21.08%

Watched Threads

View All
Latest
My Feed