You are Here: Home >< Maths

# integrating 2

Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016

1. I managed to find the integral of f'(x) in part a), but I'm stuck with part b).

I understand that the gradient of normal to P will be -1/2 and therefore, the gradient of the tangent will be +2.

However, where do I go from there? In the mark scheme, they made f'(x) equal to 2 and then => to 0, but I don't understand why.

2. (Original post by frostyy)

However, where do I go from there? In the mark scheme, they made f'(x) equal to 2 and then => to 0, but I don't understand why.

Can I please see the mark scheme? I am not sure what you mean by "then ==> to 0".
3. (Original post by frostyy)

I managed to find the integral of f'(x) in part a), but I'm stuck with part b).

I understand that the gradient of normal to P will be -1/2 and therefore, the gradient of the tangent will be +2.

However, where do I go from there? In the mark scheme, they made f'(x) equal to 2 and then => to 0, but I don't understand why.

The normal to the curve through P must pass through a point where the curve has gradient of 2. The expression gives the gradient of the curve at the point with x-coordinate , so solving will yield the x-coordinate of all points on the curve with gradient 2 (if you're careful about how you solve it to avoid spurious solutions).
4. Just solve f'(x)=2
5. (Original post by B_9710)
To go from there just solve the equations simultaneously.
2y+x=0 and y=f(x)
Not quite. We're merely told that the line is merely parallel to the normal at P, not that it's necessarily the normal at P.
6. I solved the question myself. I had to make f'(x) = 2 (since that's what the gradient for the tangent was) and then just solve for x to find its value, which was 3/2.

Thanks anyway
7. (Original post by Farhan.Hanif93)
Not quite. We're merely told that the line is merely parallel to the normal at P, not that it's necessarily the normal at P.
oh yeah. Didn't read it properly.

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 4, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams