Guest Session: 1 Question Remaining.
Create Account
to save progress.
Login
Arithmetic Sequences
hard
0:00.0
Find
d
d
d
if
S
n
=
n
(
n
+
1
)
/
2
S_n = n(n+1)/2
S
n
=
n
(
n
+
1
)
/2
.
A
1
1
1
B
2
2
2
C
0
0
0
D
None
Submit Answer