Question 614524
Y = x^3 - 3x^2 - 9x - 5 
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It looks like f(-1) = 0
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Use synthetic division to see.
-1)....1....-3....-9....-5
........1.....-4...-5...|..0


Quotient: x^2 -4x-5
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Factor the quotient:
(x-5)(x+1)

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Final factored form: (x+1)^2(x-5)
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Note: The fastest way to find one or more
Real Number zeroes is to graph the function
with a graphing calculator.  Hopefully you
have a graphing calculator, if you are studying
calculus.
Cheers,
Stan H.