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How to go about finding the real zeros of a function when given an imaginary zero?
http://www.sosmath.com/cyberexam/precalc/EA4001/EA...
its number 12 specifically but you dont need to do the problem with specific steps for me. just tell me general directions of what to do? thanks.
1 Answer
- ?Lv 71 decade agoFavorite Answer
If a zero is x1=2i the onother zero is x2= -2i ( See remainder Theo)
Then 2x^4 -x^3+7x^2 -4x-4 is exactly divided by (x-2i ) ( x-(-2i)) or by
(x^2+4)
2x^4 -x^3+7x^2 -4x-4 :(x^2+0x+ 4) = 2x^2-x-1
Then 2x^4 -x^3+7x^2 -4x-4 = (x^2+4) (2x^2-x-1) =0
ie, 2x^2-x-1 =0
x= (1+-sqrt(9))/4
x3= 1
x4= -1/2