be found arithmetic series
3a2-a6=-a2
a3+a4=19
an=ao +n*d
a2=ao+2d
a6=ao+6d
a3=ao+3d
a4=ao+3d
substutite all those, and find ao, and d.
3a2-a6=-a2
a3+a4=19
a2=ao+2d
a6=ao+6d
a3=ao+3d
a4=ao+3d
substutite all those, and find ao, and d.