Question

5x ao quadrado -20 =0

Answer 1

$5x^{2} - 20 = 0$
Δ $= 0^{2} - 4.5.(-20)$
Δ $= 0 + 400$
Δ = 400

$x = \frac{-0 +- \sqrt{400}}{2.5}$
$x = \frac{-0 +- 20}{10}$

$x^{1} = \frac{-0+20}{10} = 2$
$x^{2} = \frac{-0-20}{10} = -2$

Espero ter ajudado!