Question

Encontre as raízes das equações:
a)x²+2x=0
b)x²+2x=3
c)2x²=5
d)2x²=16

Answer 1

a)
x² + 2x = 0
x(x + 2) = 0
x = 0

x + 2 = 0
x = - 2

R.: x = 0 e x = - 2
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b)
x² + 2x = 3
x² + 2x - 3 = 0
a = 1; b = 2; c = - 3

Δ = b² - 4ac
Δ = 2² - 4.1.(-3)
Δ = 4 + 12
Δ = 16

x = - b +/- √Δ  = - 2 +/- √16
           2a                2.1

x = - 2 + 4 = 2/2 = 1
          2

x = - 2 - 4 = - 6/2 = - 3
         2

R.: x = 1 e x = - 3
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c)
2x² = 5
x² = 5/2
x = +/- √5/2
x = + √5/2 e x = - √5/2 
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d)
2x² = 16
x² =16/2
x² = 8
x = √8
x = √4.√2
x = +/- 2√2

R.: x = 2√2 e x = - 2√2