How many nonnegative integers are there such that there will be no possible ordered quintuples of nonnegative integers (not necessarily distinct) that will satisfy the equation
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We can use modulo 8 to solve this problem.
In modulo 8 , if x is an even number, x 1 2 = x 1 0 = x 8 = x 6 = x 4 = 0 ( m o d 8 ) .
In the other hand if x is an odd number, x 1 2 = x 1 0 = x 8 = x 6 = x 4 = 1 ( m o d 8 ) .
When n > 2 , 2 n = 0 ( m o d 8 ) and 2 n − 1 = − 1 ( m o d 8 ) = 7 ( m o d 8 )
Using these facts we can now solve the problem.
In modulo 8 , a 1 2 + b 1 0 + c 8 + d 6 + e 4 can only be equal to 0 , 1 , 2 , 3 , 4 , and 5 ( m o d 8 ) .
Since 2 n − 1 = 7 ( m o d 8 ) , n cannot be greater than 2 .
If n is equal to 0 , 1 , or 2 , there will be ordered quintuples ( a , b , c , d , e ) that will satisfy the equation.
Example: If n = 0 , ( a , b , c , d , e ) = ( 0 , 0 , 0 , 0 , 0 )
If n = 1 , ( a , b , c , d , e ) = ( 0 , 0 , 0 , 0 , 1 )
If n = 2 , ( a , b , c , d , e ) = ( 0 , 0 , 1 , 1 , 1 )
Therefore, n = 0 , 1 , 2 are the only possible values of n .
Since there are 2 0 1 4 nonnegative integers less than 2 0 1 4 and 3 of them are the only possible values of n . Therefore there are 2 0 1 4 − 3 = 2 0 1 1 nonnegative integer values of n such that there will be no possible ordered quintuples of nonnegative integers ( a , b , c , d , e ) that will satisfy the equation.