Originally Posted by

**thyrgle** The function is:

$\displaystyle

4x^4+17x^2+4 = 0

$

I have tried to do the following:

$\displaystyle

x^2(4x^2+17) + 4 = 0

$

$\displaystyle

x^2(4x^2+17) = -4

$

$\displaystyle

x^2 = -4

$

$\displaystyle

x = 2i

$

$\displaystyle

4x^2+17 = -4

$

$\displaystyle

4x^2 = -21

$

$\displaystyle

x^2 = -21/4

$

$\displaystyle

x^2 = sqrt(-21)/2

$

But I know I do not have the right answer for there is not sqrt(-21)/2 as one of the answers in the back of the book. Any help would be appreciated.