Question

Resolva as equações do 2° grau : a) 2x² = 18 b) x² = 729 c) 441 = x² d) x² - 5 = 620 e) 3x² - 100 = 200 *

Answer 1

Resposta:

a) 2x² = 18

${x}^{2} = \frac{18}{ 2} \\ \\ {x }^{2} = 9 \\ x = \sqrt{9} \\ x = 3$

b) x² = 729

$x = \sqrt{729} \\ x = 27$

c) 441 = x²

$441 - {x}^{2} = 0 \\ - {x}^{2} = - 441 \times ( - 1) \\ {x}^{2} = \sqrt{441} \\ x = 21$

d) x² - 5 = 620

${x }^{2} = 620 + 5 \\ {x}^{2} = 625 \\ x = \sqrt{625} \\ x = 25$

e) 3x² - 100 = 200

$3 {x}^{2} = 200 + 100 \\ 3 {x}^{2} = 300 \div 3 \\ {x }^{2} = 100 \\ x = \sqrt{100} \\ x = 10$