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Question 0501a
Sigma Notation
Method of Differences I
Question
Generate new
Find, in terms of
n
,
{n,}
n
,
∑
r
=
1
n
(
f
(
r
)
−
f
(
r
+
1
)
)
,
\sum_{r=1}^n \Big( f(r) - f(r+1) \Big),
r
=
1
∑
n
(
f
(
r
)
−
f
(
r
+
1
)
)
,
given that
f
(
0
)
=
9
,
{f(0)=9,}
f
(
0
)
=
9
,
f
(
1
)
=
7
{f(1)=7}
f
(
1
)
=
7
and
f
(
2
)
=
4.
{f(2)=4.}
f
(
2
)
=
4.
Attempt
The answer is of the form
f
(
n
−
1
)
−
a
{f(n-1) - a}
f
(
n
−
1
)
−
a
f
(
n
)
−
a
{f(n) - a}
f
(
n
)
−
a
f
(
n
+
1
)
−
a
{f(n+1) - a}
f
(
n
+
1
)
−
a
a
−
f
(
n
−
1
)
{a - f(n-1)}
a
−
f
(
n
−
1
)
a
−
f
(
n
)
{a - f(n)}
a
−
f
(
n
)
a
−
f
(
n
+
1
)
{a - f(n+1)}
a
−
f
(
n
+
1
)
where
a
=
{a=}
a
=
Answer
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