Matematika A - 2013. ljeto, 7.

$3-9+27-81+\dots 3-9+27-81+\backslash ldots$

$6+12+24+48+\dots 6+12+24+48+\backslash ldots$

$8-12+18-27+\dots 8-12+18-27+\backslash ldots$

$125+75+45+27+\dots 125+75+45+27+\backslash ldots$