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Mathematics
Problem
In any geometric progression, which of the following is always equal to
a
n
−
2
a
n
+
2
a_{n-2}\,a_{n+2}
a
n
−
2
a
n
+
2
? a)
a
n
+
1
2
a_{n+1}^{\,2}
a
n
+
1
2
b)
a
n
2
a_n^{\;2}
a
n
2
c)
a
n
a
n
+
1
a_n\,a_{n+1}
a
n
a
n
+
1
d)
a
n
a
n
+
2
a_n\,a_{n+2}
a
n
a
n
+
2
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