Help would be appreciated(:
Find all the zeros of of the equation
-3x^4+27x^2+1200=0

Question

Help would be appreciated(:
Find all the zeros of  of the equation 
-3x^4+27x^2+1200=0

timaashorty · Answer

@satellite73

timaashorty · Answer

oh there you are (:

anonymous · Answer

start by finding the zeros of 
$$-3u^2+27u+1200=0$$ where $u=x^2$

anonymous · Answer

best bet is to divide all by $-3$ and start with 
$$u^2-9u-400=0$$

anonymous · Answer

by some miracle this one actually factors as 
$$(u+16)(u-25)=0$$ and so $u=-16$ or $u=25$
now go back to $x^2$ and write 
$$x^2=-16$$ or $$x^2=25$$

timaashorty · Answer

So I would have to write it like this 

-3x^4+27(-16)^2+1200=0 ?

Or x^2= were my finall answers ?

anonymous · Answer

no your job is to solve for $x$ not rewrite it
you have 
$$x^2=25$$ so 
$$x=\pm5$$ and also 
$$x^2=-16$$ which is not possible with real numbers

timaashorty · Answer

Oh isee !

Thank you very much for the help! (:

anonymous · Answer

yw

timaashorty · Answer

Thank you timo (: