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Question 0516
Sigma Notation
2016 Paper 1 Question 6 Variant
Question
Generate new
A sequence
u
0
,
u
1
,
u
2
,
…
{u_0, u_1, u_2, \ldots}
u
0
,
u
1
,
u
2
,
…
is given by
u
0
=
7
and
u
n
=
u
n
−
1
+
n
2
+
n
\begin{gather*} u_0 = 7 \textrm{ and} \\ u_n = u_{n-1} + n^2 + n \end{gather*}
u
0
=
7
and
u
n
=
u
n
−
1
+
n
2
+
n
for
n
≥
1.
{n \geq 1.}
n
≥
1.
(i)
Find
u
1
,
u
2
{u_1, u_2}
u
1
,
u
2
and
u
3
.
{u_3.}
u
3
.
[2]
It is further given that
∑
r
=
1
n
r
(
r
+
1
)
=
n
3
(
n
+
1
)
(
n
+
2
)
.
\sum_{r=1}^n r(r+1) = {\textstyle \frac{n}{3}} (n+1)(n+2).
r
=
1
∑
n
r
(
r
+
1
)
=
3
n
(
n
+
1
)
(
n
+
2
)
.
(ii)
By considering
∑
r
=
1
n
(
u
r
−
u
r
−
1
)
,
{\displaystyle \sum_{r=1}^n (u_r - u_{r-1}),}
r
=
1
∑
n
(
u
r
−
u
r
−
1
)
,
find a formula for
u
n
{u_n}
u
n
in terms of
n
.
{n.}
n
.
[3]
Answer
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