SOLUTION: x^4+9x^3+12x^2-11x+21=0 solve the equation in the real number solution

 

Hi,

x^4+9x^3+12x^2-11x+21=0    |Note: -3 is a root

using Synthetic Divsion

-3	1	 9	 12	 -11   21

 	 	-3	-18	  18  -21

 	1	 6	-6	   7    0

yields:

      x^3 + 6x^2 - 6x + 7 = 0    |Note:  -7 is a root

using Synthetic Divsion

-7	1	 6	-6	 7   

 	 	-7	7	 -7  

 	1	 -1	1	  0 

yields:

      x^2 - x + 1 = 0