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D( r )
(r-7)/(56*r^2-(8*r^3)) = 0
56*r^2-(8*r^3) = 0
(r-7)/(56*r^2-(8*r^3)) = 0
(r-7)/(56*r^2-(8*r^3)) = 0
(r-7)/(56*r^2-8*r^3) = 0
56*r^2-8*r^3 = 0
8*r^2*(7-r) = 0
7-r = 0 // - 7
-r = -7 // * -1
r = 7
8*r^2*(r-7) = 0
(r-7)/(8*r^2*(r-7)) = 0
r-7 = 0 // + 7
r = 7
56*r^2-(8*r^3) = 0
56*r^2-(8*r^3) = 0
56*r^2-8*r^3 = 0
56*r^2-8*r^3 = 0
8*r^2*(7-r) = 0
7-r = 0 // - 7
-r = -7 // * -1
r = 7
8*r^2 = 0
8*r^2 = 0 // : 8
r^2 = 0
r = 0
r in (-oo:0) U (0:7) U (7:+oo)
((1/6)*r)/((r-7)/(56*r^2-(8*r^3))) = 0
((1/6)*r)/((r-7)/(56*r^2-8*r^3)) = 0
(1/6*r*(56*r^2-8*r^3))/(r-7) = 0
56*r^2-8*r^3 = 0
8*r^2*(7-r) = 0
7-r = 0 // - 7
-r = -7 // * -1
r = 7
8*r^2*(r-7) = 0
(1/6*8*r*r^2*(r-7))/(r-7) = 0
( 1/6*r )
1/6*r = 0 // : 1/6
r = 0
( 8*r^2 )
8*r^2 = 0 // : 8
r^2 = 0
r = 0
( r-7 )
r-7 = 0 // + 7
r = 7
r in { 0}
r in { 7}
r belongs to the empty set
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