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D( z )
z = 0
z = 0
z = 0
z in (-oo:0) U (0:+oo)
(z-(5/7))/z = (1/7)*z // - (1/7)*z
(z-(5/7))/z-((1/7)*z) = 0
(z-5/7)/z+(-1/7)*z = 0
(z-5/7)/z-z/7 = 0
(7*(z-5/7))/(7*z)+(-z*z)/(7*z) = 0
7*(z-5/7)-z*z = 0
7*z-z^2-5 = 0
7*z-z^2-5 = 0
7*z-z^2-5 = 0
DELTA = 7^2-(-5*(-1)*4)
DELTA = 29
DELTA > 0
z = (29^(1/2)-7)/(-1*2) or z = (-29^(1/2)-7)/(-1*2)
z = (29^(1/2)-7)/(-2) or z = (29^(1/2)+7)/2
(z-((29^(1/2)-7)/(-2)))*(z-((29^(1/2)+7)/2)) = 0
((z-((29^(1/2)-7)/(-2)))*(z-((29^(1/2)+7)/2)))/(7*z) = 0
((z-((29^(1/2)-7)/(-2)))*(z-((29^(1/2)+7)/2)))/(7*z) = 0 // * 7*z
(z-((29^(1/2)-7)/(-2)))*(z-((29^(1/2)+7)/2)) = 0
( z-((29^(1/2)+7)/2) )
z-((29^(1/2)+7)/2) = 0 // + (29^(1/2)+7)/2
z = (29^(1/2)+7)/2
( z-((29^(1/2)-7)/(-2)) )
z-((29^(1/2)-7)/(-2)) = 0 // + (29^(1/2)-7)/(-2)
z = (29^(1/2)-7)/(-2)
z in { (29^(1/2)+7)/2, (29^(1/2)-7)/(-2) }
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