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Meilleure réponse !
2014-01-23T10:40:57+01:00
Bonjour

1)  x^2+x-12=0\\\\\Delta=1^2-4\times1\times(-12)=49\\\\x_1=\dfrac{-1-\sqrt{49}}{2}=-4\\\\x_2=\dfrac{-1+\sqrt{49}}{2}=3\\\\S=\{-4;3\}


2) 3x^2+2x+6=0\\\\\Delta=2^2-4\times3\times6=-68<0\\\\S=\phi


3) -32x + 64x² + 4 = 0
64x² - 32x + 4 = 0
16x² - 8x + 1 = 0
(4x - 1)² = 0
4x - 1 = 0
4x = 1
x = 1/4

S = {1/4} 

4) 2x^2=2x+4\\\\2x^2-2x-4=0\\\\x^2-x-2=0\\\\\Delta=(-1)^2-4\times1\times(-2)=9\\\\x_1=\dfrac{1-\sqrt{9}}{2}=-1\\\\x_2=\dfrac{1+\sqrt{9}}{2}=2\\\\S=\{-1;2\}