Question

2,7,12,17........
a) Aflati termenul de pe locul 27
b) aflati suma primilor 35 de numere!!
Rezolvare+explicate va rog! Dau coroana​

Answer 1

$\it a_1=2+5\cdot0 \\ a_2=2+5\cdot1\\a_3=2+5\cdot2\\a_3=2+5\cdot3\\.\\.\\.\\a_n=2+5\cdot(n-1)\\.\\.\\.\\a_{27}=2+5\cdot26\\.\\.\\.\\a_{35}=2+5\cdot34\\ --------\\S=35\cdot2+5(1+2+3+\ ...\ +34)$