/ progresii 6 Alegeţi formula corectă pentru S_n suma primilor n termeni ai unei progresii aritmetice «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msub»«mi mathvariant=¨normal¨»a«/mi»«mn»1«/mn»«/msub»«mo»,«/mo»«mo»§#160;«/mo»«msub»«mi mathvariant=¨normal¨»a«/mi»«mn»2«/mn»«/msub»«mo»,«/mo»«mo»§#160;«/mo»«mo».«/mo»«mo».«/mo»«mo».«/mo»«mo»§#160;«/mo»«mo»,«/mo»«mo»§#160;«/mo»«msub»«mi mathvariant=¨normal¨»a«/mi»«mi mathvariant=¨normal¨»n«/mi»«/msub»«/math» cu raţia r.

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]]> Răspuns corect!

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]]> Răspuns greşit!

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