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5 la 0+.........+5 la 2004

Răspuns :

[tex]A=5^0+5+5^2+...+5^{2004}|(-5)\\ -5A=-5-5^2-5^3-...-5^{2005}\\ .........................................\\ -4A=5^0-5^{2005}\\ -4A=1-5^{2005} \\ 4A=5^{2005}-1\\ A=\frac{5^{2005}-1}{4}[/tex]
S=5^0+5^1+5^2+5^3+...+5^2004  / X5
5 X S = 5^1+5^2+5^3+...+ 5^2004+5^2005
   se scad relatiile (de os in sus)
5xS -S = 5^2005 - 1           (5^2005=5)
4X S =  5-1
4 X S = 4
S= 4:4
S=1