Answer:
1/6
Step-by-step explanation:
sequence should be 1/6,1/3,1/2,2/3
common difference=1/3-1/6=2/6-1/6=1/6
or 1/2-1/3=(3-2)/6=1/6
or c.d.=2/3-1/2=(4-3)/6=1/6
Answer:
a21 = -61
Step-by-step explanation:


(subtract to eliminate a₁)
9 = -3d
d = -3
-19 = a₁ + (6)(-3)
-1 = a
a21 = -1 + (21 - 1)(-3)
= -61
The average is 4 and the standard deviation is 0.34. :)