7. (+1) (n+3 (n+3)(n+2) 2 for n ≥ -1
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
Related questions
Question
Can you please help with #7 and #9? TIA
![Justify the equations in 6-9 either by deriving them from for-
mulas in Example 9.7.1 or by direct computation from Theo-
rem 9.5.1. Assume m, n, k, and r are integers.
6. (m+k₁) -
= m + k, for m+k≥ 1
1
n+3
7. (+³)
=
(n+3)(n+2)
2
, for n ≥ -1
n+1
8.
(7) = 1, for k-r≥0
k
r
2n
9.
(²2)
for n ≥ 0
n](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F7259b638-946e-4297-aa49-7ff3a18fa479%2Fe1ec6aa1-8e2d-48d7-bc62-f9091391d960%2Fgj3s86_processed.png&w=3840&q=75)
Transcribed Image Text:Justify the equations in 6-9 either by deriving them from for-
mulas in Example 9.7.1 or by direct computation from Theo-
rem 9.5.1. Assume m, n, k, and r are integers.
6. (m+k₁) -
= m + k, for m+k≥ 1
1
n+3
7. (+³)
=
(n+3)(n+2)
2
, for n ≥ -1
n+1
8.
(7) = 1, for k-r≥0
k
r
2n
9.
(²2)
for n ≥ 0
n
![Theorem 9.7.1 Pascal's Formula
Let n and r be positive integers and suppose r ≤n. Then
n+
(" + ¹) = ( ² ) + ( ) ·
r
Proof (algebraic version):
Let n and r be positive integers with r ≤n. By Theorem 9.5.1,
n!
( ²₁ ) + ( )=
+
(r − 1)!(n − (r − 1))!
-
r!(n-r)!
n!
n!
+
(r − 1)!(n − r + 1)!r!(n-r)!*
To add these fractions, a common denominator is needed, so multiply the numera-
tor and denominator of the left-hand fraction by r and multiply the numerator and
denominator of the right-hand fraction by (n-r+1). Then
n!
r
n!
(²₁) + ( )
(r − 1)!(n −r + 1)! r
(n-r+1)
r!(n-r)! (nr+1)
n-n! -n!-r+n!
n!.r
(n-r+1)!r(r 1)!
(nr+1)(n-r)!r!
_n!+r+n!•n__n!r+n!
=
n!(n + 1)
(n+1-r)!r!
(n-r+1)!r!
(n + 1)!
=
((n + 1) -r)!r!
=
= ("+¹).](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F7259b638-946e-4297-aa49-7ff3a18fa479%2Fe1ec6aa1-8e2d-48d7-bc62-f9091391d960%2Fpgdgz97_processed.png&w=3840&q=75)
Transcribed Image Text:Theorem 9.7.1 Pascal's Formula
Let n and r be positive integers and suppose r ≤n. Then
n+
(" + ¹) = ( ² ) + ( ) ·
r
Proof (algebraic version):
Let n and r be positive integers with r ≤n. By Theorem 9.5.1,
n!
( ²₁ ) + ( )=
+
(r − 1)!(n − (r − 1))!
-
r!(n-r)!
n!
n!
+
(r − 1)!(n − r + 1)!r!(n-r)!*
To add these fractions, a common denominator is needed, so multiply the numera-
tor and denominator of the left-hand fraction by r and multiply the numerator and
denominator of the right-hand fraction by (n-r+1). Then
n!
r
n!
(²₁) + ( )
(r − 1)!(n −r + 1)! r
(n-r+1)
r!(n-r)! (nr+1)
n-n! -n!-r+n!
n!.r
(n-r+1)!r(r 1)!
(nr+1)(n-r)!r!
_n!+r+n!•n__n!r+n!
=
n!(n + 1)
(n+1-r)!r!
(n-r+1)!r!
(n + 1)!
=
((n + 1) -r)!r!
=
= ("+¹).
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Thank you. Can you please explain why you multiplied by 2! in the denominator in step 2? How does that 2! get there?
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