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Help with this short core 1 question

Its from edexcel jan 07

Its a long question about arithmetic progression but you end up with this

(3k-100)(k+35)<0

It asks to work out the value of k. (2 marks)

The answer is 100/3.

Why is it only one bracket that has been used though? Shouldn't the other bracket be used too to get an answer of -35?
Reply 1
Original post by Insanity514
Its from edexcel jan 07

Its a long question about arithmetic progression but you end up with this

(3k-100)(k+35)<0

It asks to work out the value of k. (2 marks)

The answer is 100/3.

Why is it only one bracket that has been used though? Shouldn't the other bracket be used too to get an answer of -35?


because the answer cannot be negative so you only consider the positive solution
(you can't have a negative number of rows)
(edited 13 years ago)
Reply 2
Original post by Insanity514
Its from edexcel jan 07

Its a long question about arithmetic progression but you end up with this

(3k-100)(k+35)<0

It asks to work out the value of k. (2 marks)

The answer is 100/3.

Why is it only one bracket that has been used though? Shouldn't the other bracket be used too to get an answer of -35?


Well it depends on what "k" is supposed to represent. Most likely because it cannot be negative, but that's dependant on what "k" actually is.
Reply 3

Thanks guys

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