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Byju's Answer
Standard XIII
Mathematics
Binomial Coefficients
For 2 ≤ r ≤ n...
Question
For
2
≤
r
≤
n
,
(
n
r
)
+
2
(
n
r
−
1
)
+
(
n
r
−
2
)
is equal to
A
(
n
+
1
r
−
1
)
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B
(
n
+
1
r
+
1
)
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C
2
(
n
+
2
r
)
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D
(
n
+
2
r
)
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Solution
The correct option is
D
(
n
+
2
r
)
(
n
r
)
+
2
(
n
r
−
1
)
+
(
n
r
−
2
)
=
[
(
n
r
)
+
(
n
r
−
1
)
]
[
(
n
r
−
1
)
+
(
n
r
−
2
)
]
=
(
n
+
1
r
)
+
(
n
+
1
r
−
1
)
=
(
n
+
2
r
)
[
∵
n
C
r
+
n
C
r
−
1
=
n
+
1
C
r
]
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0
Similar questions
Q.
For
2
≤
r
≤
n
,
(
n
r
)
+
2
(
n
r
−
1
)
+
(
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−
2
)
is equal to
Q.
For
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≤
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,
(
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)
+
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(
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+
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Q.
For
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n
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)
+
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(
r
−
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n
)
+
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−
2
n
)
Q.
For
2
≤
r
≤
n
,
(
n
+
1
r
)
+
(
n
r
−
1
)
+
(
n
r
−
2
)
is equal to-
Q.
Shew that the highest power of
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