Back
to top
A-Level Maths Question Differentiation help
Watch
Announcements
Page 1 of 1
Go to first unread
Skip to page:
A curve has the equation y=ln3x-e^-2x. Show that the equation of the tangent at the point with an X coordinate of 1 is: y=[(e^2 2)/e^2]x - [(e^2 3)/e^2] ln3I've differentiated and got gradient as (2/e^2) 1... where do I go from here as curve doesnt cross y-axis so cant use y=mx c and can't use y-y1=m(x-x1) because I dont have any y co-ords ? Any help would be great thanks
0
reply
(Original post by Export kid)
Sub in x=1 to the original eqn to get a y coordinate
Sub in x=1 to the original eqn to get a y coordinate
(Original post by CaptainDuckie)
How can you find y coordinate if x is 1?
How can you find y coordinate if x is 1?
Last edited by annonymous2394; 4 weeks ago
0
reply
Report
#5
(Original post by annonymous2394)
Thanks for replies but answer i get is off what Im trying to prove.. I've attached some photos so u know where I'm at
Thanks for replies but answer i get is off what Im trying to prove.. I've attached some photos so u know where I'm at
So what now
0
reply
Report
#6
When x = 1, mx+c=m+c. Compare with the value of y when x = 1 to find c and rearrange to get it in the same form as the question is asking for.
You should not use a calculator during this question btw.
You should not use a calculator during this question btw.
1
reply
Thanks for the help !
I've now got y=((2/e^2)+ 1)x - ((e/e^2 )+1 ) + ln3
its close but somehow need to add the 1 in the brackets to the 2/e^2 bit ? so that it looks the same as what im trying to prove
(this is the bit I was confused about at the start when I first got the gradient as its not the same )?
I've now got y=((2/e^2)+ 1)x - ((e/e^2 )+1 ) + ln3
its close but somehow need to add the 1 in the brackets to the 2/e^2 bit ? so that it looks the same as what im trying to prove
(this is the bit I was confused about at the start when I first got the gradient as its not the same )?
0
reply
(Original post by DFranklin)
To add the 1 in the first bracket, rewrite 1 as e^2 / e^2
To add the 1 in the first bracket, rewrite 1 as e^2 / e^2
0
reply
(Original post by annonymous2394)
Thats what i initially thought but doesnt that make the bottom of the fraction 2e^2 instead of just e^2
Thats what i initially thought but doesnt that make the bottom of the fraction 2e^2 instead of just e^2
0
reply
(Original post by annonymous2394)
wait i am an idiot
wait i am an idiot
Last edited by annonymous2394; 4 weeks ago
0
reply
Report
#12
(Original post by annonymous2394)
wait i am an idiot
wait i am an idiot
(Original post by annonymous2394)
lol cant believe it that was dumb of me I get it now thanks for the help have a good day
lol cant believe it that was dumb of me I get it now thanks for the help have a good day
It’s normal to get things wrong.
0
reply
0
reply
Report
#14
(Original post by annonymous2394)
hahaha no i know I find it quite funny just wasn't thinking properly!
hahaha no i know I find it quite funny just wasn't thinking properly!
0
reply
X
Page 1 of 1
Go to first unread
Skip to page:
Quick Reply
