Question

qual o resultado 5x²+20=0

Answer 1

$5x\²+20=0\\\\5x\² =-20\\\\x\² =-20/5\\\\x\² =-4\\\\x =\pm\sqrt{-4}\\\\\boxed{S=\{\varnothing\}\text{ (sem raiz real)}}\\\\\\\text{Ou, usando o conjunto dos complexos:}\\\\x^{2}=-4\\\\x=\sqrt{-4}\\\\x=\pm2i\\\\\boxed{S=\{-2i,2i\}}$