I am trying to find out if the polynomial 12x^4+8x^3+9x^2+4x+4 is reducible or irreducible over Q. We can't apply Eisenstein's criterion here. But we can try this: 12x^4+8x^3+9x^2+4x+4 = x^4+(2/3)x^3+(3/4)x^2+(1/3)x+(1/3) x^4+(2/3)x^3+(3/4)x^2+(1/3)x+(1/3)=(x^2+ax+b)(x^2+cx+d) = x^4+(a+c)x^3+(b+d+ac)x^2+(ad+dc)x+bd We get the equation system: a+c=(2/3) b+d+ac=(3/4) ab+bc=(1/3) bd=(1/3) I get the following result: b=(1/2) d=(2/3) c=(2+sqrt(19))/6 and (2-sqrt(19))/6 a=(2/3)-((2+sqrt(19))/6) and (2/3)-((2-sqrt(19))/6) The expression in a contains an irrational number, sqrt(19), this means that the polynomial is irreversible over Q. Is this correct?
I am trying to find out if the polynomial 12x^4+8x^3+9x^2+4x+4 is reducible or irreducible over Q. We can't apply Eisenstein's criterion here. But we can try this: 12x^4+8x^3+9x^2+4x+4 = x^4+(2/3)x^3+(3/4)x^2+(1/3)x+(1/3) x^4+(2/3)x^3+(3/4)x^2+(1/3)x+(1/3)=(x^2+ax+b)(x^2+cx+d) = x^4+(a+c)x^3+(b+d+ac)x^2+(ad+dc)x+bd We get the equation system: a+c=(2/3) b+d+ac=(3/4) ab+bc=(1/3) bd=(1/3) I get the following result: b=(1/2) d=(2/3) c=(2+sqrt(19))/6 and (2-sqrt(19))/6 a=(2/3)-((2+sqrt(19))/6) and (2/3)-((2-sqrt(19))/6) The expression in a contains an irrational number, sqrt(19), this means that the polynomial is irreversible over Q. Is this correct?
Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter1: Fundamental Concepts Of Algebra
Section: Chapter Questions
Problem 5DE
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I am trying to find out if the polynomial 12x^4+8x^3+9x^2+4x+4 is reducible or irreducible over Q.
We can't apply Eisenstein's criterion here.
But we can try this:
12x^4+8x^3+9x^2+4x+4 = x^4+(2/3)x^3+(3/4)x^2+(1/3)x+(1/3)
x^4+(2/3)x^3+(3/4)x^2+(1/3)x+(1/3)=(x^2+ax+b)(x^2+cx+d) = x^4+(a+c)x^3+(b+d+ac)x^2+(ad+dc)x+bd
We get the equation system:
a+c=(2/3)
b+d+ac=(3/4)
ab+bc=(1/3)
bd=(1/3)
I get the following result:
b=(1/2)
d=(2/3)
c=(2+sqrt(19))/6 and (2-sqrt(19))/6
a=(2/3)-((2+sqrt(19))/6) and (2/3)-((2-sqrt(19))/6)
The expression in a contains an irrational number, sqrt(19), this means that the polynomial is irreversible over Q.
Is this correct?
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