solve; find all real and imaginary solutions in exact form. x^4-9x^2-10=0

Question

solve; find all real and imaginary solutions in exact form.  x^4-9x^2-10=0

anonymous · Answer

maybe easier to start with 
$$u^2-9u-10=0$$ find the two solutions, then replace $u$ by $x^2$ and solve for $x$

anonymous · Answer

find the dicriminent then the roots of 4x^2-2x+4=0

anonymous · Answer

not to bad since $$u^2-9u-10$$ factors as 
$$(u-10)(u+1)$$ so you can easily solve 
$$(u-10)(u+1)=0$$

anonymous · Answer

that makes sense!

anonymous · Answer

thanks!

anonymous · Answer

yw

anonymous · Answer

so I got 10 and -1 but when you plug both of them back in, neither of them work

anonymous · Answer

of course they do 
they work for $$u^2-9u-10=0$$ but not for the original equation 
now you have to solve 
$$x^2=10$$ and also $x^2=-1$

anonymous · Answer

ohhhh! I see ok

anonymous · Answer

both are easy, the second one gives you the two complex solutions

anonymous · Answer

yea, I see what I did wrong, I plugged it into the wrong equation. thanks!

anonymous · Answer

so to find $$x^2=10$$ and $$x^2=-1$$ you have to take the square root of each side?