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Question 1013833:  4.6
 
The following function is given.
 
f(x)=x^3 -5x^2 -9x+45
 
a. List all rational zeros that are possible according to the Rational Zero Theorem:
 
b. Use synthetic division to test several possible rational zeros in order to identify one actual zero 
   One rational zero of the given function is: 
 
c. Use the zero from part (b) to find all the zeros of the polynomial function 
   The zeros of the function f(x)=x^3-5x^2 -9x+45 is: 
 Answer by Boreal(15235)      (Show Source): 
You can  put this solution on YOUR website! x^3 -5x^2 -9x+45=0 
rational zeros are +/- 1,3,5,9,15,and 45, the factors of the constant divided by the factors of x^3. 
using synthetic division with 3. By looking at the division, 1 did not look like it would work, so I went to 3.  If that didn't work, I would try -3. Then I would try 5 or -5. 
1;;;;-5;;;;-9;;;;-45 
1;;;;-2;;;;-15---0 
Therefore,(x-3) is a factor, and what is left over is  x^2-2x+15.  That factors to (x-5)(x+3).   
roots are -3,3, and 5. 
  
 
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