# Math Help - "simple" polynomial question

1. ## "simple" polynomial question

"simple" polynomial question, any help would be appreciated

Show that (x-1)(x-2) is a factor of

P(x) = x^n (2^m -1) + x^m(1-2^n) + (2^n - 2^m)

m and n are positive integers

2. Well if the expressions $x-2$ and $x-1$ are factors of the given polynomial, $x=1$ and $x=2$ must be its roots.

So just substitute $x=1$ and then $x=2$ and see if the equation

$x^n(2^m-1) + x^m(1-2^n) + 2^n-2^m = 0$ is satisfied.

so for $x=1$ , the value of the polynomial is,
$2^m-1+1-2^n+2^n-2^m=0$

Hence the above equation is satisfied. So x-1 is a factor.

Now, insert $x=2$ and prove that the value of the polynomial becomes zero.

so as x=1 and x=2 are the roots of the given polynomial $(x-1)(x-2)$ is a factor.

3. can you check that again though, cause im pretty sure (x-1)(x-2) is a quadratic

4. It is. But by proving that x=1 and x=2 are the roots of the given polynomial, it follows that x-1 and x-2 are factors. Hence their product,
(x-1)(x-2) will also be a factor.