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A level maths

http://prntscr.com/16c3kg7 Help please as I am confused.
Is it 8i-2j+ai+bj+ai-bj=0? Please show me the working out
Original post by helpplease346
http://prntscr.com/16c3kg7 Help please as I am confused.
Is it 8i-2j+ai+bj+ai-bj=0? Please show me the working out

What did you get as the values for a and b?
Original post by helpplease346
http://prntscr.com/16c3kg7 Help please as I am confused.
Is it 8i-2j+ai+bj+ai-bj=0? Please show me the working out

Check the bit in bold above.
Original post by laurawatt
What did you get as the values for a and b?

a=-8
B i dont know
Original post by Plücker
Check the bit in bold above.

Becomes 8i-2j +2ai=0 (bj-bj becomes nothing)
Original post by helpplease346
a=-8

Not quite, you’re almost there. When you split up what you wrote in your first post into just the ‘i’ component you get 8i+ai+ai=0, so 8i+2ai=0
Original post by helpplease346
Becomes 8i-2j +2ai=0 (bj-bj becomes nothing)

Plücker is wanting you to look at the F3 in the question, then look at what you’ve written for F3 :smile:
Original post by laurawatt
Not quite, you’re almost there. When you split up what you wrote in your first post into just the ‘i’ component you get 8i+ai+ai=0, so 8i+2ai=0

oh a=-4
Then for b idk
Original post by helpplease346
oh a=-4
Then for b idk

Yeah that’s good :smile:
So to find b we do the same thing as we did to find a, but we focus on the ‘j’ component instead , give it a try and post what you get?
Original post by laurawatt
Yeah that’s good :smile:
So to find b we do the same thing as we did to find a, but we focus on the ‘j’ component instead , give it a try and post what you get?

b=3 ?
Original post by helpplease346
b=3 ?

Yep :smile:
Original post by laurawatt
Yep :smile:

Thank you.
Part B)will be
-8i+2j (F1 is reversed) -4i+3j +-4i-j
= -16i +4j is the answer for part B?
Original post by laurawatt
Yep :smile:

is part b -16i+4j ? Thank you for the help
Original post by helpplease346
is part b -16i+4j ? Thank you for the help

Yep think so :biggrin:

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