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Polynomial Functions

by josephcollins
Tags: functions, polynomial
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josephcollins
#1
Jun19-04, 05:47 PM
P: 60
Could someone please help me with this question, I'd be most obliged:

Q) Find the value of "a" for which the function
2x^3 - ax^2 - 12x - 7
has a repeated factor.

Thanks
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Gokul43201
#2
Jun19-04, 06:40 PM
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If you mean two identical roots, then ...

write [tex] 2x^3 - ax^2 - 12x - 7 = (x-b)^2(2x-c) [/tex]

Expand the RHS and compare coefficients. You have 3 equations in 3 unknowns.
robert Ihnot
#3
Jul4-04, 12:59 AM
P: 1,059
Since we are seeking only a specific solution, we can keep in mind that if the cubic has a double root, that this root is also present in its derative. The derative is: 2(3X^2-aX-6). Here if we let a =3, we get X =2, -1. -1 works in the original equation and the factoring then is 2(x+l)^2(x-7/2).


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