You are Here: Home >< Maths

# URGENT maths help!!!! Watch

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.

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:
Updated: May 26, 2016
Today on TSR

### Falling in love with him

But we haven't even met!

### Top study tips for over the Christmas holidays

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.