Salutare!
Te folosesti de factorul comun si vei grupa termeni in paranteze in asa fel incat sa iti dea in paranteze 13
[tex]\bf B = 1+3^{1} +3^{2} +3^{3} +3^{4} +.......... +3^{114} +3^{115} +3^{116}[/tex]
[tex]\bf B=(1+3^{1} +3^{2}) +3^{3}\cdot(3^{0}+3^{1} +3^{2})+3^{6}\cdot(3^{0}+3^{1} +3^{2})+....... +3^{114}\cdot(3^{0}+3^{1} +3^{2})[/tex]
[tex]\bf B = 13 +3^{3}\cdot 13+3^{6}\cdot 13 +3^{9}\cdot 13+.......... +3^{114}\cdot 13[/tex]
[tex]\bf B = 13\cdot(1+3^{3}+3^{6} +3^{9}+.......... +3^{114})[/tex] ⋮ 13
Mult succes !
