Question

Resolva:

a) 2x² - 18 = 0
b) x² = 400
c) x² + 5 = 30

​

Answer 1

Resposta:

a)

$2x^2-18=0\\ \\ 2x^2=18\\ \\ x^{2} =18\div2\\ \\ x^{2} =9\\ \\ x=\pm\sqrt{9} \\ \\ x=\pm3\\ \\ S=\{-3,+3\}$

--------------------------------------

b)

$x^{2} =400\\ \\ x=\pm\sqrt{400} \\ \\ x=\pm20\\ \\ S=\{-20,+20\}$

-------------------------------------

c)

$x^2+5=30\\ \\ x^2=30-5\\ \\ x^2=25\\ \\ x=\pm\sqrt{25} \\ \\ x=\pm5\\ \\ S=\{-5,+5\}$