Question

calcule a15 da P.A (-2,-3,-4....)

Answer 1

$a_n=a_{15}=? \\ a_1=-2 \\ r-3-(-2)=-3+2=-1 \\ n=15 \\ \\ termo~~geral \\ \\ a_n=a_1+(n-1)r \\ \\ a_{15}=-2+(15-1)(-1) \\ \\ a_{15}=-2+(14)(-1) \\ \\ a_{15}=-2-14 \\ \\\fbox{ a_{15}=-16 }$