2017 here I come!

Algebra Level 4

Let P P be a monic polynomial of degree 2017 such that P ( 1 ) = P ( 2 ) = = P ( 2016 ) = 0 P(1) = P(2) = \cdots = P(2016) = 0 and P ( 0 ) = 2018 ! P(0) = 2018! .

Find the largest root of P ( x ) P(x) .


Notation: ! ! is the factorial notation. For example, 8 ! = 1 × 2 × 3 × × 8 8! = 1\times2\times3\times\cdots\times8 .


The answer is 2016.

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3 solutions

Fidel Simanjuntak
Jan 22, 2017

Since P ( 1 ) = P ( 2 ) = P ( 3 ) = . . . = P ( 2016 ) = 0 P(1)= P(2) = P(3) = ... = P(2016) =0 , we can see that 1 , 2 , 3 , . . . , 2016 {1,2,3,...,2016} are the roots of P ( x ) P(x) . Then, the largest root of P ( x ) P(x) is 2016 2016 .

A polynomial of degree 2017 2017 which has the numbers from 1 1 to 2016 2016 as roots cam be P ( x ) = ( x 1 ) ( x 2 ) ( x 3 ) ( x 2016 ) ( x a ) P(x)=(x-1)(x-2)(x-3)\cdots(x-2016)(x-a) P ( 0 ) = a 2016 ! = 2018 ! a = 2017 2018 \Rightarrow P(0)=-a\cdot 2016! =2018! \Rightarrow a=-2017\cdot 2018 Then the other root must be negative, so the greatest root is 2016 2016

Abhishek Alva
Jan 13, 2017

It's given that P(x) is a polynomial of degree 2008, u also know 20016 roots of P(x) ....(which are 1,2,3.....2016) let the other root be m P(x) can be written as (x-1)(x-2)(x-3)(x-4)......(x-2016)(x-m ) .....now Use P(0) = 2009! when we plug P(0) we get the value 2017*2018=4070306

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