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D( x )
x-3 = 0
x^2-9 = 0
x+3 = 0
x-3 = 0
x-3 = 0
x-3 = 0 // + 3
x = 3
x^2-9 = 0
x^2-9 = 0
1*x^2 = 9 // : 1
x^2 = 9
x^2 = 9 // ^ 1/2
abs(x) = 3
x = 3 or x = -3
x+3 = 0
x+3 = 0
x+3 = 0 // - 3
x = -3
x in (-oo:-3) U (-3:3) U (3:+oo)
7/(x-3)+2/(x+3) = (-2*x)/(x^2-9) // - (-2*x)/(x^2-9)
7/(x-3)+2/(x+3)-((-2*x)/(x^2-9)) = 0
7/(x-3)+2/(x+3)+2*x*(x^2-9)^-1 = 0
7/(x-3)+2/(x+3)+(2*x)/(x^2-9) = 0
(7*(x+3)*(x^2-9))/((x-3)*(x+3)*(x^2-9))+(2*(x-3)*(x^2-9))/((x-3)*(x+3)*(x^2-9))+(2*x*(x-3)*(x+3))/((x-3)*(x+3)*(x^2-9)) = 0
7*(x+3)*(x^2-9)+2*(x-3)*(x^2-9)+2*x*(x-3)*(x+3) = 0
9*x^3+2*x^3+15*x^2-81*x-18*x-135 = 0
11*x^3+15*x^2-99*x-135 = 0
11*x^3+15*x^2-99*x-135 = 0
11*x^3+15*x^2-99*x-135
15*(x^2-9)+11*x^3-99*x
11*x*(x^2-9)+15*(x^2-9)
(11*x+15)*(x^2-9)
((11*x+15)*(x^2-9))/((x-3)*(x+3)*(x^2-9)) = 0
((11*x+15)*(x^2-9))/((x-3)*(x+3)*(x^2-9)) = 0 // * (x-3)*(x+3)*(x^2-9)
(11*x+15)*(x^2-9) = 0
( 11*x+15 )
11*x+15 = 0 // - 15
11*x = -15 // : 11
x = -15/11
( x^2-9 )
1*x^2 = 9 // : 1
x^2 = 9
x^2 = 9 // ^ 1/2
abs(x) = 3
x = 3 or x = -3
x in { 3}
x in { -3}
x = -15/11
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