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D( k )
k = 0
k = 0
k = 0
k in (-oo:0) U (0:+oo)
5.2/k+81.9 = 47.2 // - 47.2
5.2/k-47.2+81.9 = 0
5.2*k^-1 = -34.7 // : 5.2
k^-1 = -6.67307692
-1 < 0
1/(k^1) = -6.67307692 // * k^1
1 = -6.67307692*k^1 // : -6.67307692
-0.14985591 = k^1
k = -0.14985591
k = -0.14985591
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