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D( x )
48-(3*x^2) = 0
48-(3*x^2) = 0
48-(3*x^2) = 0
48-3*x^2 = 0
-3*x^2 = -48 // : -3
x^2 = 16
x^2 = 16 // ^ 1/2
abs(x) = 4
x = 4 or x = -4
x in (-oo:-4) U (-4:4) U (4:+oo)
(x^2+3*x-28)/(48-(3*x^2)) = 0
(x^2+3*x-28)/(48-3*x^2) = 0
x^2+3*x-28 = 0
x^2+3*x-28 = 0
DELTA = 3^2-(-28*1*4)
DELTA = 121
DELTA > 0
x = (121^(1/2)-3)/(1*2) or x = (-121^(1/2)-3)/(1*2)
x = 4 or x = -7
(x+7)*(x-4) = 0
((x+7)*(x-4))/(48-3*x^2) = 0
( x+7 )
x+7 = 0 // - 7
x = -7
( x-4 )
x-4 = 0 // + 4
x = 4
x in { 4}
x = -7
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