B.T.

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If (x+y)^m has 3 consecutive coefficients in A.P.,then a possible value of m(here mEN) may be equal to:

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3 Answers

11

Joydoot ghatak ·2011-03-14 21:49:35

i m getting,
m = 4n+1Â±√8n+92

where n can take any value which is less than m...

there are many such pairs...

but if we take n=9...
we get m=14 and 23..

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Vinay Arya ·2011-03-15 02:50:53

How to get the first result?What is n?m=14,7 are the answers.

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11

Joydoot ghatak ·2011-03-15 04:01:28

take ^mC_n-1,^mC_n and ^mC_n+1 are the co-effients that are in A.P.

simplify it...

u will get the above result after some bad calculations...

u need to see that m and n can not be a fraction or irrational.
accordingly we have to assign the value of n to get m.
thus (8n+9) should be a perfect square.
take n=2, we get m=7 and take n=9 we get m=14.

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