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Calculati: [tex]1+(1+i)+(1+i)^2+...+(1+i) ^{2n-1} [/tex], n∈N, i∈C.
Mersi


Răspuns :

fie 1+i=x
[tex] 1+x+ x^{2} + x^{3} +.............+ x^{2n-1} =S/x \\ x+ x^{2} + x^{3} +.................... x^{2n} =Sx \\ \\ x^{2n} -1=S(x-1) \\ S= \frac{ x^{2n} -1}{x-1} = \f \frac{( 1+i)^{2n}-1 }{i} [/tex]