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2010-03-31T10:24:54+02:00
A)2x2-3x-9=0
4x-3x-9=0
-x=9/:(-1)
x=-9

b)x2-8x+12=0
2x-8x+12=0
-6x=-12/:(-6)
x=2
2010-03-31T10:28:01+02:00
A)2x²-3x-9=0


Δ=b²-4ac=(-3)²-4*2*(-9)=9+71=81
√Δ=√81=9

x₁=(-b+√Δ)/2a=(9+9)/2=18/2=9
x₂=(-b-√Δ)/2a=(9-9)/2=0/2=0

b)x²-8x+12=0

Δ=b²-4ac=(-8)²-4*1*12=64-48=16
√Δ=√16=4

x₁=(-b+√Δ)/2a=(8+4)/2=12/2=6
x₂=(-b-√Δ)/2a=(8-4)/2=4/2=2
2010-03-31T10:37:10+02:00
2x2 - 3x - 9 = 0
4x - 3x = 9
x = 9

x2 - 8x + 12 = 0
2x - 8x = -12
-6x = -12 / : (-6)
x = 2