Question

Calcule as raízes da equação 2.(x + 5).x = 300

Answer 1

Resposta:

2x + 10 - 300 = 0
2x - 290 = 0
x = 290/2
x = 145

Avalia por favor.

Answer 2

$2(x + 5) \: . \:x = 300 \\ (x + 5) \: . \: x = \frac{300}{2} \\ (x + 5) \: . \: x = 150 \\ x {}^{2} + 5x = 150 \\ x {}^{2} + 5x - 150 = 0 \\ \boxed{a = 1 \: ,\: b = 5 \: , \: c = - 150} \\ x = \frac{ - b ± \sqrt{b {}^{2} - 4ac } }{2a} \\ x = \frac{ - 5 ± \sqrt{5 {}^{2} - 4 \: . \: 1 \: . \: ( - 150)} }{2 \: . \: 1} \\ x = \frac{ - 5 ± \sqrt{25 + 600} }{2} \\ x = \frac{ - 5 ± \sqrt{625} }{2} \\ x = \frac{ - 5 ± 25}{2} \\ x = \frac{ - 5 + 25}{2} = \frac{20}{2} = \boxed{\boxed{\boxed{10}}} \\ x = \frac{ - 5 - 25}{2} = \frac{ - 30}{2} = \boxed{\boxed{\boxed{ - 15}}}$

att. yrz