Question

4x ao quadrado +64=0 sem usa e baskara

Answer 1

$4 x^{2} +64=0\to\\ \\ 4 x^{2} =-64\to\\\\ x^{2} =- \dfrac{64}{4} \to\\\\ x^{2} =-16\to\\\\ x=\pm~ \sqrt{-16} \\\\\\ N\~ao~~tem~~rai\´zes~~dentro~~dos~~reais,~~mas~~tem~~nos~~complexos;$



$Sendo \sqrt{-1} =i\\\\x=\pm~ \sqrt{-1\times16}\to\\\\ x=\pm~ \sqrt{-1}\times \sqrt{16} \to\\\\ x=\pm~ i\times4\to\\\\ x=\pm~ 4i\\\\\\\\ \large\boxed{\boxed{S=\{-4i~;~4i\}}}$

Answer 2

4x²+64=0
4x²=-64
x²=-16
x=-4