Integration

Hi, please could i have help on this question. I have attached my working below with the answers and question but on the answer it says to integrate again which i did but on the markscheme the -7x wasn’t integrated? I don’t understand why.
Here is the question and answer and my working:
https://app.gemoo.com/share/image-annotation/598208046202937344?codeId=MpEwb1NW0z84r&origin=imageurlgenerator

Thank you!

Reply 1

mqb2766

From the first integration
c = -7
and when you integrate that again its -7x. Your
dy/dx = ... - 7x + k
is incorrect as that part of the expression should just be -7 so no "x" and no "+k".

(edited 4 months ago)

Reply 2

anonymous294

Original post by mqb2766

From the first integration
c = -7
and when you integrate that again its -7x. Your
dy/dx = ... - 7x + k
is incorrect as that part of the expression should just be -7 so no "x" and no "+k".