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calculează 2supra 13 +4supra13 +6supra13+....104supra 13
5supra 41 +10supra 41+15 supra41+....200supra41


Calculează 2supra 13 4supra13 6supra13104supra 13 5supra 41 10supra 4115 Supra41200supra41 class=

Răspuns :

2/13 + 4/13 + 6/13 + ... + 104/13 = (2+4+6+...+104)/13 = 2(1+2+3+...+52)/13 = [2(53*52)/2]/13 = 53*52/13 = 53*4 = 212

5/41 + 10/41 + 15/41 + ... + 200/41 = (5+10+15+...+200)41 = 5(1+2+3+...+40)/41 = [5(41*40)/2]/41 = 5*41*20/41 = 5*20 = 100