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D( x )
65-x = 0
65-x = 0
65-x = 0
65-x = 0 // - 65
-x = -65 // * -1
x = 65
x in (-oo:65) U (65:+oo)
0.2 = (x^2)/(65-x) // - (x^2)/(65-x)
0.2-((x^2)/(65-x)) = 0
(-1*x^2)/(65-x)+0.2 = 0
(-1*x^2)/(65-x)+(0.2*(65-x))/(65-x) = 0
0.2*(65-x)-1*x^2 = 0
13-x^2-0.2*x = 0
13-x^2-0.2*x = 0
13-x^2-0.2*x = 0
DELTA = (-0.2)^2-(-1*4*13)
DELTA = 0.2^2+52
DELTA = 52.04
DELTA > 0
x = ((0.2^2+52)^(1/2)+0.2)/(-1*2) or x = (0.2-(0.2^2+52)^(1/2))/(-1*2)
x = ((0.2^2+52)^(1/2)+0.2)/(-2) or x = (0.2-(0.2^2+52)^(1/2))/(-2)
(x-(((0.2^2+52)^(1/2)+0.2)/(-2)))*(x-((0.2-(0.2^2+52)^(1/2))/(-2))) = 0
((x-(((0.2^2+52)^(1/2)+0.2)/(-2)))*(x-((0.2-(0.2^2+52)^(1/2))/(-2))))/(65-x) = 0
((x-(((0.2^2+52)^(1/2)+0.2)/(-2)))*(x-((0.2-(0.2^2+52)^(1/2))/(-2))))/(65-x) = 0 // * 65-x
(x-(((0.2^2+52)^(1/2)+0.2)/(-2)))*(x-((0.2-(0.2^2+52)^(1/2))/(-2))) = 0
( x-(((0.2^2+52)^(1/2)+0.2)/(-2)) )
x-(((0.2^2+52)^(1/2)+0.2)/(-2)) = 0 // + ((0.2^2+52)^(1/2)+0.2)/(-2)
x = ((0.2^2+52)^(1/2)+0.2)/(-2)
( x-((0.2-(0.2^2+52)^(1/2))/(-2)) )
x-((0.2-(0.2^2+52)^(1/2))/(-2)) = 0 // + (0.2-(0.2^2+52)^(1/2))/(-2)
x = (0.2-(0.2^2+52)^(1/2))/(-2)
x in { ((0.2^2+52)^(1/2)+0.2)/(-2), (0.2-(0.2^2+52)^(1/2))/(-2) }
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