SOLUTION: what is Value of x; when x3-x=990

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Question 618969: what is Value of x; when x3-x=990
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

what is Value of x

x^3-x=990

x^3-x -990 = 0         Note:  x+=+10 is one solution   1000-10 -990 = 0  

Using synthetic division  

   10	1	0	-1	-990

		10	100	990

	1	10	99	0

(x-10)(x^2 + 10x + 99)

(x^2 + 10x + 99)

x+=+%28-10+%2B-+sqrt%28+100-396%29%29%2F%282%29+

x+=+%28-10+%2B-+sqrt%28+296%29%29%2F%282%29+

x+=+%28-10+%2B-+2sqrt%28+74%29%29%2F%282%29+

x+=+-5+%2B-+8.6023+

 ONe real solution, x = 10 and two imaginary solutions