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D( t )
t^2 = 0
t^2 = 0
t^2 = 0
1*t^2 = 0 // : 1
t^2 = 0
t = 0
t in (-oo:0) U (0:+oo)
(0.135*260)/298 = (0.79*140)/(t^2) // - (0.79*140)/(t^2)
(0.135*260)/298-((0.79*140)/(t^2)) = 0
(0.135*260)/298-110.6*t^-2 = 0
-110.6*t^-2 = -0.11778523 // : -110.6
t^-2 = 0.00106497
-2 < 0
1/(t^2) = 0.00106497 // * t^2
1 = 0.00106497*t^2 // : 0.00106497
938.99358667 = t^2
t^2 = 938.99358667 // ^ 1/2
abs(t) = 938.99358667^(1/2)
t = 938.99358667^(1/2) or t = -938.99358667^(1/2)
t in { 938.99358667^(1/2), -938.99358667^(1/2) }
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