If
x = 1 + 2 0 1 4 2 + 2 0 1 4 4 + 2 0 1 4 8 + ⋯ + 2 0 1 4 2 2 0 1 3
Then, the value of ( x x + 1 ) 9 5 can be expressed in the form b 2 a , where a and b are positive coprime integers. What is the value of a + b ?
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One should not simply borrow questions from SMO.
Anyway, multiply the equation by 2 0 1 4 2 .
Now, taking this and subtracting the original, we get ( 2 0 1 4 2 − 1 ) x = 1 . So now 1 + x 1 = 2 0 1 4 2 and hence, we get our conclusion of 111
Yea sorry I didn't state that it is adapted from SMO :/
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Let q = 2 0 1 4 2 . Then x = q 2 0 1 3 + q 2 0 1 2 + q 2 0 1 1 + ⋯ + q + 1 = q − 1 q 2 0 1 4 − 1 = 2 0 1 4 2 − 1 1 . We have therefore ( x x + 1 ) 9 5 = ( 1 + x 1 ) 9 5 = ( 1 + 2 0 1 4 2 − 1 ) 9 5 = 2 0 1 4 2 9 5 . And, finally, since 2 0 1 4 = 1 9 ⋅ 1 0 6 and 9 5 = 1 9 ⋅ 5 , 2 0 1 4 2 9 5 = 1 0 6 2 5 , and a + b = 1 1 1 .