Question

X ao quadrado mais 20x igual a 300

Answer 1

X² + 20x = 300
X² + 20x - 300 = 0

Δ= b² - 4ac
Δ= 20² - 4 . 1 . (-300)
Δ= 400 + 1200
Δ= 1600

X= - 20 ± √1600 / 2 . 1
X= - 20 ± 40 / 2
X'= - 20 + 40 / 2 = 20 / 2 = 10
X"= - 20 - 40 / 2 = - 60 / 2 = - 30

S={ 10 e -30 }

Answer 2

${x}^{2} + 20x = 300 \\ {x}^{2} + 20x - 300 = 0$

$a = 1 \\ b = 20 \\ c = ( - 300)$

$\Delta = {b}^{2} - 4ac \\ \Delta = {20}^{2} - 4 \times 1 \times ( - 300) \\ \Delta = 400 + 1200 \\ \Delta = 1600$

$x = \frac{ - b\pm \sqrt{\Delta} }{2a} \\ \\ x = \frac{ - 20\pm \sqrt{1600} }{2 \times 1} \\ \\ x = \frac{ - 20\pm40}{2}$

$x_{1} = \frac{ - 20 + 40}{2} = \frac{20}{2} = 10 \\ \\ x_{2} = \frac{ - 20 - 40}{2} = - \frac{60}{2} = - 30$

$S = \{ - 30,10 \}$