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Four is a zero of the equation x^3+3x^2−18x−40=0.

Which factored form is equivalent to the equation?

 

A.  (x+2)(x−√4)(x+√4)=0

 

B.  (x−4)(x+2)(x+5)=0

 

C.  (x+4)(x+2)(x+5)=0

 

D.  (x−4)(x+4)(x+5)=0

 Sep 25, 2018
edited by Guest  Sep 25, 2018

Best Answer 

 #1
avatar+6252 
+1

if four is a zero then (x-4) is a factor

 

so we divide x3+3x218x40 by (x4)to determine what the other factors might be.x3+3x218x40x4=x2+7x+10

 

This quotient is easy enough to factor as x2+7x+10=(x+5)(x+2)and thusx3+3x218x40=(x4)(x+2)(x+5)this is choice B

 Sep 25, 2018
 #1
avatar+6252 
+1
Best Answer

if four is a zero then (x-4) is a factor

 

so we divide x3+3x218x40 by (x4)to determine what the other factors might be.x3+3x218x40x4=x2+7x+10

 

This quotient is easy enough to factor as x2+7x+10=(x+5)(x+2)and thusx3+3x218x40=(x4)(x+2)(x+5)this is choice B

Rom Sep 25, 2018

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