[Fan + Medal] Find all of the zeros of the equation: -3x^4 + 27x^2 + 1200 = 0.

Please don't just give the answer, work it out!

Question

[Fan + Medal] Find all of the zeros of the equation:  -3x^4 + 27x^2 + 1200 = 0.

Please don't just give the answer, work it out!

anonymous · Answer

need help

misty1212 · Answer

HI!!

misty1212 · Answer

put $u=x^2$  and solve $$-3u^2+27u+1200=0$$ for $u$

priyar · Answer

yeah..now its simply a quad eq..

misty1212 · Answer

probably easiest to divide by $-3$ next, get $$u^2-9u-400=0$$

anonymous · Answer

misty1212 · Answer

then if you are lucky it factors

ltrout · Answer

@misty1212 Why do we change x^2 to u?

misty1212 · Answer

because you can always solve a quadratic equation

misty1212 · Answer

then change back at the end
you don't really have to do that, if you know how to factor $$  -3x^4 + 27x^2 + 1200
$$

misty1212 · Answer

it is just a gimmick to see it easily

ltrout · Answer

Okay @misty1212 , I got it:). Could you help on one more?

misty1212 · Answer

i gotta run to class now
good luck