Let f(x) = axm + am-prm-1 + . . . + a, and g(x) = b,x"+ b,-px"-1 + ... + bo belong to Q[x] and suppose that f(x)g(x) belongs to Z[x]. Prove that a,b; is an integer for every i and j.

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter4: Polynomial And Rational Functions
Section4.2: Properties Of Division
Problem 52E
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Let f(x) = axm + am-prm-1 + . . . + a, and g(x) = b,x"+ b,-px"-1 +
... + bo belong to Q[x] and suppose that f(x)g(x) belongs to Z[x].
Prove that a,b; is an integer for every i and j.
Transcribed Image Text:Let f(x) = axm + am-prm-1 + . . . + a, and g(x) = b,x"+ b,-px"-1 + ... + bo belong to Q[x] and suppose that f(x)g(x) belongs to Z[x]. Prove that a,b; is an integer for every i and j.
Expert Solution
Step 1

Given that,

f(x)=amxm+am-1xm+....+a0Q[x]g(x)=bnxn+bn-1xn-1+....+b0Q[x]

This implies that ai,biQ.

Suppose, fxgxZx.

By Gauss' Lemma, since fxgx factors in Zx, so there exists q,r such that:

q,rQ

and,

qfxZxqaiZrgxZxrbjZ

and,

qr=1

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