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D( x )
x^2+6*x-40 = 0
x^2+6*x-40 = 0
x^2+6*x-40 = 0
x^2+6*x-40 = 0
DELTA = 6^2-(-40*1*4)
DELTA = 196
DELTA > 0
x = (196^(1/2)-6)/(1*2) or x = (-196^(1/2)-6)/(1*2)
x = 4 or x = -10
x in (-oo:-10) U (-10:4) U (4:+oo)
(3*x-12)/(x^2+6*x-40) = 0
x^2+6*x-40 = 0
x^2+6*x-40 = 0
DELTA = 6^2-(-40*1*4)
DELTA = 196
DELTA > 0
x = (196^(1/2)-6)/(1*2) or x = (-196^(1/2)-6)/(1*2)
x = 4 or x = -10
(x+10)*(x-4) = 0
(3*x-12)/((x+10)*(x-4)) = 0
3*x-12 = 0 // + 12
3*x = 12 // : 3
x = 12/3
x = 4
x in { 4}
x belongs to the empty set
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