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determinati numarul real x pentru care x la puterea a 2 +12 x+31

Răspuns :

2×2+12×X+31=
4+12×X=31
12×X=31-4
12×X=27
X=27:12
X=2+3
X=5
X²+12X+31=0
a=1
b=12
c=31
Δ=b²-4ac⇒Δ=(12)²-4×1×31⇒Δ=144-124⇒Δ=20⇒√Δ=√20=Δ=2√5
x1x2=-b+-√Δ/2a
x1=-12+2√5/2⇒x1=-6+2√5
x2=-12-2√5/2⇒x2=-6-2√5
sucees