The number N = 2 3 3 − 2 1 9 − 2 1 7 − 1 has exactly one divisor between 1000 and 5000. Which divisor is that?
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its factors are: 3^(3) * 13 * 661 * 37021
so the answer => 3*661=1983
using calculator?? I did that way actually :p
BTW, the problem maker must be a cricket lover and an Indian... ;)
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What! You checked all the numbers from 1000 to 5000??
????? please clarify
I can't understand ?
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Since its the first time India won world cup
Isn't this a number theory problem?
1 2 3 4 |
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1, 3, 9, 13, 27, 39, 117, 351, 661, 1983, 5949, 8593, 17847, 25779, 37021, 77337, 111063, 232011, 333189, 481273,
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This is my soluction for the problem:
A , B and C are the roots of x 3 − ( A + B + C ) X 2 + ( A B + A C + B C ) x + A B C = 0
So, when we make x = A , x = B and x = C the sentence is true:
A 3 − ( A + B + C ) A 2 + ( A B + A C + B C ) A − A B C = 0 (I)
B 3 − ( A + B + C ) B 2 + ( A B + A C + B C ) B − A B C = 0 (II)
C 3 − ( A + B + C ) C 2 + ( A B + A C + B C ) C − A B C = 0 (III)
Adding (I) + (II) + (III) we get:
( A 3 + B 3 + C 3 ) − 3 A B C = ( A + B + C ) ( A 2 + B 2 + C 2 ) + ( A + B + C ) ( A B + A C + B C )
( A 3 + B 3 + C 3 ) − 3 A B C = ( A + B + C ) ( A 2 + B 2 + C 2 + A B + A C + B C )
This is a well known factorization.
Now lets make:
2 3 3 = ( 2 1 1 ) 3 ;
− 2 1 9 = − 2 × 2 1 8 = − 2 1 8 − 2 1 8 = ( − 2 6 ) 3 − 2 × 2 1 7
− 2 1 7 = − 2 1 1 × 2 6
Now lets look the original expression:
2 3 3 − 2 1 9 − 2 1 7 − 1
and lets re write it as:
( 2 1 1 ) 3 + ( − 2 6 ) 3 + ( − 1 3 ) − 3 × 2 1 1 × ( − 2 6 ) × ( − 1 )
Making A = 2 1 1 ; B = − 2 6 and C = − 1 we get:
( 2 1 1 ) 3 + ( − 2 6 ) 3 + ( − 1 3 ) − 3 × 2 1 1 × ( − 2 6 ) × ( − 1 ) = ( 2 1 1 − 2 6 − 1 ) ( A 2 + B 2 + C 2 − A B − A C − B C ) = 1 9 8 3 × ( A 2 + B 2 + C 2 − A B − A C − B C )
So 1983 is the wanted divisor.
Thanks for all who shared and liked :-)