Question

Rezultatul calculului 1 supra 1×5 + 1 supra 5×9 + 1 supra 9 ×13 +...+1 supra 105× 109 este: a. 27 supra 109 b. 108 supra 109 c.1 d.2

Answer 1

4/1×5=1/1-1/5
4/1×5×9=1/5-1/9
(4/1×5+4/5×9+4/9×13+.......+4/105×109):4=
(1/1-1/15+.....................+1/105-109):4=
1/1-1/109):4=
[109-1/109]:4=
27/109