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Quick FP2 question

For this question,

how was I supposed to know that 2/3 wouldn't get cancelled out? I know that you can just try do it in your mind by subbing in values into the equations and seeing if at any point it cancels out but this method is long winded (especially in this case where I'd have to test out 9 equations). I'm just asking for a more efficient method really..

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There's not even a pattern in the way they cancel out:

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Original post by creativebuzz
For this question,

how was I supposed to know that 2/3 wouldn't get cancelled out? I know that you can just try do it in your mind by subbing in values into the equations and seeing if at any point it cancels out but this method is long winded (especially in this case where I'd have to test out 9 equations). I'm just asking for a more efficient method really..

Untitled (2).png

There's not even a pattern in the way they cancel out:

Attachment not found


Scan the lines diagonally, matching up common denominators, and sum along the lines. You need to keep terms until you hit a zero sum.

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Original post by ghostwalker
Scan the lines diagonally, matching up common denominators, and sum along the lines. You need to keep terms until you hit a zero sum.

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Why are you matching the denominators?
Original post by creativebuzz
Why are you matching the denominators?


You're looking for terms that will cancel to zero in the partial sums. They don't have to match - it's just a guide. As long as you can see the diagonals clearly.
(edited 7 years ago)
Original post by ghostwalker
You're looking for terms that will cancel to zero in the partial sums. They don't have to match - it's just a guide. As long as you can see the diagonals clearly.


I don't see how that makes it obvious that 2/3 isn't cancelled out
Original post by creativebuzz
I don't see how that makes it obvious that 2/3 isn't cancelled out


Sum of first diagonal is ....

Sum of second diagonal is ....

Sum of third diagonal is....
and all subsequent ones, until towards the end.

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