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D( x )
x^2-x-12 = 0
x-4 = 0
x+3 = 0
x^2-x-12 = 0
x^2-x-12 = 0
x^2-x-12 = 0
DELTA = (-1)^2-(-12*1*4)
DELTA = 49
DELTA > 0
x = (49^(1/2)+1)/(1*2) or x = (1-49^(1/2))/(1*2)
x = 4 or x = -3
x-4 = 0
x-4 = 0
x-4 = 0 // + 4
x = 4
x+3 = 0
x+3 = 0
x+3 = 0 // - 3
x = -3
x in (-oo:-3) U (-3:4) U (4:+oo)
7/(x^2-x-12)+4/(x+3) = 1/(x-4) // - 1/(x-4)
7/(x^2-x-12)+4/(x+3)-(1/(x-4)) = 0
7/(x^2-x-12)+4/(x+3)-(x-4)^-1 = 0
7/(x^2-x-12)+4/(x+3)-1/(x-4) = 0
x^2-x-12 = 0
x^2-x-12 = 0
x^2-x-12 = 0
DELTA = (-1)^2-(-12*1*4)
DELTA = 49
DELTA > 0
x = (49^(1/2)+1)/(1*2) or x = (1-49^(1/2))/(1*2)
x = 4 or x = -3
(x+3)*(x-4) = 0
7/((x+3)*(x-4))+4/(x+3)-1/(x-4) = 0
7/((x+3)*(x-4))+(4*(x-4))/((x+3)*(x-4))+(-1*(x+3))/((x+3)*(x-4)) = 0
4*(x-4)-1*(x+3)+7 = 0
4*x-x-9-3 = 0
3*x-12 = 0
(3*x-12)/((x+3)*(x-4)) = 0
(3*x-12)/((x+3)*(x-4)) = 0 // * (x+3)*(x-4)
3*x-12 = 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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