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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
(x+100)/2 = (25*x+300)/x // - (25*x+300)/x
(x+100)/2-((25*x+300)/x) = 0
(x+100)/2+(-1*(25*x+300))/x = 0
(x*(x+100))/(2*x)+(-1*2*(25*x+300))/(2*x) = 0
x*(x+100)-1*2*(25*x+300) = 0
x^2+50*x-600 = 0
x^2+50*x-600 = 0
x^2+50*x-600 = 0
DELTA = 50^2-(-600*1*4)
DELTA = 4900
DELTA > 0
x = (4900^(1/2)-50)/(1*2) or x = (-4900^(1/2)-50)/(1*2)
x = 10 or x = -60
(x+60)*(x-10) = 0
((x+60)*(x-10))/(2*x) = 0
((x+60)*(x-10))/(2*x) = 0 // * 2*x
(x+60)*(x-10) = 0
( x+60 )
x+60 = 0 // - 60
x = -60
( x-10 )
x-10 = 0 // + 10
x = 10
x in { -60, 10 }
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