Question

What are the real and complex roots of -3x^4 + 27x^2 + 1200?

Answer 1

`-3x^4 + 27x^2 + 1200=0\\ x^4-9x^2-400=0\\ x^4-25x^2+16x^2-400=0\\ x^2(x^2-25)+16(x^2-25)=0\\ (x^2+16)(x^2-25)=0\\ (x^2+16)(x-5)(x+5)=0\\ x=-4i \vee x=4i \vee x=-5 \vee =5`