You are Here: Home >< Maths

# URGENT maths help!!!!

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. I got this answer to a vectors question but I tried it a different way and got a different answer and I'm not sure what I've done wrong
First part of the question is -a+b and that's right
Next I did OP= OB + 1/4AB
=b+1/4(-a+b)
=5/4b - 1/4a
But when I did it this way OP=OA+3/4AB
=a+3/4(-a+b)
=a - 3/4a +3/4b
=1/4a +3/4b
and they aren't the same
2. Here's the question
Attached Images

3. (Original post by Purpleunicorn197)
Here's the question
Actually never mind- I got it
4. In the first way, you did it wrong. Thats why you got 5/4b - 1/4a. You're meant to subtract the 1/4(AB) because BP runs in the opposite direction to AB, so it should be negative.

(Edit: Sorry, I only made this post during the time you worked it out so I didn't see you got it, apologies xD)
5. The first method you used, OP = OB + 1/4 AB, you need to use 1/4 BA not AB, because you're going the other way, so instead of using AB = -a+b you need to use BA (which is effectively negative AB), which would be a-b or b + -a

Hope that helps and good luck today!
6. The second way is correct and the answer should be -1/4a + 3/4b.
This is because when you did the first way you accidently did OP = OB +1/4AB.
However if you look at the diagram, you were supposed to do 1/4BA, which is why you ended up with two different values.

## 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: May 26, 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