Behaviour being used: Adaptive mode
Minimum fraction: 0
Question summary: Alegeţi formula corectă pentru Sn suma primilor n termeni ai unei progresii aritmetice [straight a subscript 1 comma space straight a subscript 2 comma space... space comma space straight a subscript straight n] cu raţia r.: [straight S subscript straight n equals fraction numerator open square brackets straight a subscript 1 plus open parentheses straight n minus 1 close parentheses straight r close square brackets times straight n over denominator 2 end fraction]; [straight S subscript straight n equals fraction numerator open square brackets 2 straight a subscript 1 plus open parentheses straight n minus 1 close parentheses straight r close square brackets times straight n over denominator 3 end fraction]; [straight S subscript straight n equals fraction numerator open square brackets 2 straight a subscript 1 plus open parentheses straight n minus 1 close parentheses straight r close square brackets times straight n over denominator 2 end fraction]
Right answer summary: [straight S subscript straight n equals fraction numerator open square brackets 2 straight a subscript 1 plus open parentheses straight n minus 1 close parentheses straight r close square brackets times straight n over denominator 2 end fraction]
Question state: todo