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Define the polynomial ring $\Bbb Q[c][x]$.Find the $c$ values where $x^2 + x + c + 1$ has a double root.

asked 2019-07-25 15:00:01 +0100

anonymous user

Anonymous

updated 2019-07-29 15:04:22 +0100

FrédéricC gravatar image

Sage question: Define the polynomial ring $\Bbb Q[c][x]$.Find the $c$ values where $x^2 + x + c + 1$ has a double root. Sage code I have found.

K.<c>=QQ['c']

R.<x>=K[]

f=x^2+x+c+1

f

How do I find the code for the $c$ values where $x^2 + x + c + 1$ has a double root. Also, can you give some examples so that I can construct some programming code in sage?

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Is it homework ?

tmonteil gravatar imagetmonteil ( 2019-07-28 21:14:54 +0100 )edit

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answered 2019-07-29 14:58:39 +0100

rburing gravatar image

A polynomial has a double root iff its discriminant is zero, so:

sage: f.discriminant()
-4*c - 3
sage: f.discriminant().roots(multiplicities=False)
[-3/4]
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Asked: 2019-07-25 15:00:01 +0100

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Last updated: Jul 29 '19