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Rezolvati ecuatiile !
x la a doua+5x+4=0
2 x la a doua +8x+8=0
2xx la a doua -12x+18 =0


Răspuns :

Relatiile lui Viete:

S= -5, P= 4, -1 si -4 sunt radacinile

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simplificam prin 2:

x^2 + 4x + 4 = 0 ⇔ (x+2)^2 = 0 ⇒ x1=x2= -2(radacina dubla in -2)

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simplificam si aici prin 2:

x^2 -6x + 9 = 0 ⇔ (x-3)^2 = 0 ⇒ x1=x2=3

x² + 5 x + 4 = 0            Δ = b² - 4ac;  x₁, x₂ = ( - b + / - √Δ ) / 2a

Δ = 25 - 16 = 9

x₁ = ( - 5 + √9 ) / 2  = ( - 5 + 3 ) / 2 = -2 / 2= - 1

x₂ = ( - 5 - 3 ) / 2 = - 8 / 2 = - 4

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2 x² + 8 x + 8 = 0  l   : 2

x² + 4 x + 4 = 0

Δ = 16 - 16 = 0

Δ = 0 ⇒ x₁ = x₂= - 4 / 2 = - 2

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2 x² - 12 x + 18 = 0  l  : 2

x² - 6 x + 9 = 0

Δ = 36 - 36

Δ = 0 ⇒   x₁ = x₂ = 6 / 2 = 3