Can anyone help me out
http://www.madasmaths.com/archive/iygb_practice_papers/c4_practice_papers/c4_b.pdf
question 7

I get the mark scheme but what I want to know is WHY they've formed the differential like that. I get that (2y-150) is usually together, but can't the -5 move to the RHS to become -1/5?

Reply 2647

math42

20

Original post by qweening

Can anyone help me out
http://www.madasmaths.com/archive/iygb_practice_papers/c4_practice_papers/c4_b.pdf
question 7

I get the mark scheme but what I want to know is WHY they've formed the differential like that. I get that (2y-150) is usually together, but can't the -5 move to the RHS to become -1/5?

Does there have to be a reason..

Reply 2648

michael242103

6

Can someone please explain this from the C4 book page 52 chapter 5. How can you let lambda -alpha=0 when it says that vectors a and b are non zero vectors

Thanks

Screen Shot 2016-06-14 at 19.46.04.png32.8KB

Reply 2649

Kevin De Bruyne

21

Original post by michael242103

Can someone please explain this from the C4 book page 52 chapter 5. How can you let lambda -alpha=0 when it says that vectors a and b are non zero vectors

Thanks

If you can see the logic from the previous line, then it's just saying that since a is not parallel to b, and a and b are non zero, then their coefficients must be 0 for them to be equal, hence they get those two things at the end.

Reply 2650

michael242103

6

but if a and be are defined as non zero vectors how can the coefficient (lambda -alpha) =0 becuase then a would be a zero vector. Is it trying to say that since they are not parallel their coefficients have to equal zero for that to be legit??

Original post by SeanFM

If you can see the logic from the previous line, then it's just saying that since a is not parallel to b, and a and b are non zero, then their coefficients must be 0 for them to be equal, hence they get those two things at the end.

Reply 2651

Kevin De Bruyne

21

Original post by michael242103

but if a and be are defined as non zero vectors how can the coefficient (lambda -alpha) =0 becuase then a would be a zero vector. Is it trying to say that since they are not parallel their coefficients have to equal zero for that to be legit??

I see what you're saying.

If ka where k is a constant and a is a vector, then if a is non-zero but ka = 0 then k must be 0. ka is a 0 vector but a itself is non-zero. That last bit is what is confusing you, I think.

Reply 2652

michael242103

6

Original post by SeanFM

I see what you're saying.

If ka where k is a constant and a is a vector, then if a is non-zero but ka = 0 then k must be 0. ka is a 0 vector but a itself is non-zero. That last bit is what is confusing you, I think.

I get what youre saying here. So basically what you mean is that if you were to rearange the expression making it (lambda-alpha)a-(beta-myoo)b=0................. then the coefficients must equal zero??