Fermi
·
Concept Library
·
Courses
·
Books
·
Problems
·
Simulations
·
Math Wiki
·
High School
Fermi
›
Problems
Mathematics
Mathematics
Problem
If
a
1
a_1
a
1
is the first term,
a
n
a_n
a
n
the
n
n
n
-th term and
S
n
S_n
S
n
the sum of the first
n
n
n
terms of an arithmetic progression, which statement is always true? a)
S
n
=
n
(
a
1
+
a
n
)
S_n = n\,(a_1 + a_n)
S
n
=
n
(
a
1
+
a
n
)
b)
S
n
+
1
=
S
n
+
a
n
S_{n+1} = S_n + a_n
S
n
+
1
=
S
n
+
a
n
c)
S
n
=
n
2
(
a
1
+
a
n
)
S_n=\dfrac{n}{2}(a_1+a_n)
S
n
=
2
n
(
a
1
+
a
n
)
d)
S
n
=
n
2
(
a
n
−
a
1
)
S_n=\dfrac{n}{2}(a_n-a_1)
S
n
=
2
n
(
a
n
−
a
1
)
Browse the problem library