a) S= (8 + 8⁴³) *43/2
8¹=(.....8)
8²=(.....4)
8³=(......2)
8⁴=(.....6)
8⁵=(.......8)
se repeta din 4 in 4
43:4=10 rest 3 =>8⁴³=(.....2)
S=[8+(......2)] *43/2= (......10)*43/2= (.....5)*43= (.......5)
b)S=3⁰ +3+3² +....+3⁴²
S=1+3+3²+...+3⁴²
S=(1+3⁴²)*43/2
3¹=(.....3)
3²=(.....9)
3³=(.....7)
3⁴=(.....1)
3⁵=(.....3)
se repeta din 4 in 4
42:4=10 rest 2 =>3⁴²=(.....9)
S=[1+(....9)]*43/2= (.....10)*43/2= (.....5)*43= (.....5)
c)S=8+8¹+8²+....+8⁸⁸
S=(8+8⁸⁸)*89/2
8¹=(.....8)
8²=(.....4)
8³=(.....2)
8⁴=(.....6)
8⁵=(.....8)
se repeta din 4 in 4 88:44=2 =>8⁸⁸=(......8)
S=[8+(.....8)]*89/2= (.......16)*89/2= (....8)*89= (.....2)
