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URGENT is this correct? MATHS INTEGRATION

The gradient of the curve is given by dy/dx= (x^2+3)^2 divided by x^2, x is not 0
(A) Show that day/dx = x^2+6+9x^-2
My answer is : proven
The point. (3,20) lies on C
(B) find an equation for the curve C in the form y=f(x)
I have got:
X^2 divided by 2/3 +3/2(x^2)
Y=(x^2+6+9x^-2) +c
20= 3(x^2+6+9x^-2) +c
20= 3x^2 +18 +27x^-2 +c
3x^2+27x^-2-2+c

Reply 1

RantingWhovian

I got:

Attachment not found

(Ignore the other image that was before I saw you have a coordinate)

(edited 6 years ago)

0D5E519D-63CA-46EB-B758-9D4194C4ED94.jpg.jpeg24.8KB

Reply 2

VannR

Original post by RantingWhovian

I got:

Attachment not found

The last term is incorrect. You need to divide the 9x^(-2) by the -2, not by -1.

Reply 3

RantingWhovian

Original post by VannR

The last term is incorrect. You need to divide the 9x^(-2) by the -2, not by -1.

I don’t use a method, I just do it in my head. Surely if you differentiate -9x^-1 you get 9x^-2, so that would work??

Reply 4

VannR

Original post by RantingWhovian

I don’t use a method, I just do it in my head. Surely if you differentiate -9x^-1 you get 9x^-2, so that would work??

Hahaha yeah, you're right, the method is that you divide by the exponent plus 1.....which is -1 in this case! Please forgive, I'm a second-year mathematics student who has not integrated a simple polynomial in months :tongue:

Reply 5

Muttley79

Original post by RantingWhovian

I got:

Attachment not found

(Ignore the other image that was before I saw you have a coordinate)

+ c needed

Reply 6

RantingWhovian

Original post by Muttley79

+ c needed

I said ignore this one

Reply 7

RantingWhovian

Original post by VannR

I’ve never been taught it before 😄

Reply 8

Muttley79

Original post by RantingWhovian

I said ignore this one

So why did you leave it there? Just delete the post!

Reply 9

RantingWhovian

Original post by Muttley79

So why did you leave it there? Just delete the post!

I tried to! I’m not stupid. I had originally put it then saw the other part of OP’s post and changed my answer. I thought I’d deleted the other attachment but saw it and added the bracket. The app won’t let me delete the post