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x in (-oo:+oo)
(-15/2)*x-(3*x^2) = 0
(-15/2)*x-3*x^2 = 0
-3*x^2-15/2*x = 0
DELTA = (-15/2)^2-(-3*0*4)
DELTA = 225/4
DELTA > 0
x = ((225/4)^(1/2)+15/2)/(-3*2) or x = (15/2-(225/4)^(1/2))/(-3*2)
x = -5/2 or x = 0
x in { -5/2, 0 }
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