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rezolvati ecuatiile 3(x-1)(2x+5)=0

Răspuns :

3(x-1)(2x+5)=0
3(2x²+5x-2x-5)=0
6x²+9x-15=0
Δ=b²-4ac=9²-4*6*(-15)=81+360=441
x1,2=(-9+-√441)/2*6=(-9+-21)/12
x1=(-9+21)/12=12/*12=1
x2=(-9-21)/12=-30/12=-5/2=-2,5