sum of the coefficient of x^13.y^2 and x^2.y^13 in expansion of (x+y)^15 is
class 11 maths ch-8
Answers
Answered by
0
Answer:
Coefficient of
x
8
y
5
is
1287
Explanation:
We know
(
a
+
b
)
n
=
n
C
0
a
n
⋅
b
0
+
n
C
1
a
n
−
1
⋅
b
1
+
n
C
2
a
n
−
2
⋅
b
2
+
...
...
...
.
+
n
C
n
a
n
−
n
⋅
b
n
Here
a
=
x
,
b
=
y
,
n
=
13
We know,
n
C
r
=
n
!
r
!
⋅
(
n
−
r
)
!
x
8
⋅
y
5
will be in
6
th term
T
6
=
13
C
5
⋅
x
13
−
5
⋅
y
5
=
13
C
5
x
8
⋅
y
5
13
C
5
=
13
!
5
!
⋅
(
13
−
5
)
!
=
1287
Coefficient of
x
8
y
5
is
1287
[Ans]
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Answer:
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