Question

A soma do quadrado de um número real nega-
tivo com o seu quádruplo dá O. Qual é esse nú-
mero?

Answer 1

$\sf x^2 +4x = 0\\\\\sf \Delta=b^2-4ac\\\sf \Delta=4^2-4\cdot1\cdot0\\\sf \Delta=16\\\\\sf x = \dfrac{-b\pm\sqrt\Delta}{2a}\\\\\sf x = \dfrac{-4\pm\sqrt{16}}{2\cdot1}\\\\\sf x = \dfrac{-4\pm4}{2}\\\\\\\sf x_1 = \dfrac{-4+4}{2}=\dfrac02=0\\\\\sf x_2 = \dfrac{-4-4}{2}=\dfrac{-8}2=-4\\\\\\\boxed{\boxed{\sf S = \{0, -4\}}}$

Bons estudos.