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GCSE Higher Mathematics Vectors

Hey :smile: I have problems with vectors in terms of knowing which direction to go from in terms of the several vector laws and position vectors. My main problem is definitely knowing which direction to obtain the values from.2

http://img9.imageshack.us/img9/7676/13313514.png

Regarding Question 1, question b requires me to find AE. I started at A then I went to B then to C then to D and finally E to obtain y-x-y-x.

For C I had to obtain the answer for AC. I started at A to B then to C which I recieved -y-z, but the answer is 4x +y.

Does anyone know what I'm doing wrong? Please I need help. What can I do to prevent myself from making the same mistakes within the examination?

All comments are greatly appreciated. Many thanks :smile:
Reply 1
Avatar for ttoby
ttoby
15
You appear to be making the assumption that BA is y, which it isn't.

What you should do is use the fact that AE=3ED so since ED is x, you know that AE=3x. Then you can go from A to E to D to C.
Reply 2
Avatar for nick198929
nick198929
OP
1
Hey Ttoby. Thanks alot. But it's the same with all other Vector questions I am exposed to. I keep on making the same mistakes in terms of which direction to go in.
Reply 3
Avatar for ttoby
ttoby
15
What you need to remember is for two vectors to be the same, they need to have the same length (or magnitude) and the same direction. In your question, DC and BA had roughly the same length but their directions were different, so you couldn't say that they were the same vectors.
Reply 4
Avatar for Princestia
Princestia
9
nick198929
Hey :smile: I have problems with vectors in terms of knowing which direction to go from in terms of the several vector laws and position vectors. My main problem is definitely knowing which direction to obtain the values from.2

http://img9.imageshack.us/img9/7676/13313514.png

Regarding Question 1, question b requires me to find AE. I started at A then I went to B then to C then to D and finally E to obtain y-x-y-x.

For C I had to obtain the answer for AC. I started at A to B then to C which I recieved -y-z, but the answer is 4x +y.

Does anyone know what I'm doing wrong? Please I need help. What can I do to prevent myself from making the same mistakes within the examination?

All comments are greatly appreciated. Many thanks :smile:



Hey, could you please post the actual correct answers from the mark scheme for all questions A-D so people can help if they've got the right answer too..

Like, I've worked these out but I can't really explain them without knowing for sure if I'm right coz there's no point explaining something if it's wrong in the first place. Also, answers will help those who attempted this question and want to know if they got it right.

Thanks :smile:

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