Can you please explain to me why is (k(k+1) ) / 2 is an integer and I know it always even so can you help me prove that?
Can you please explain to me why is (k(k+1) ) / 2 is an integer and I know it always even so can you help me prove that?
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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Question
Can you please explain to me why is (k(k+1) ) / 2 is an integer and I know it always even so can you help me prove that?
![15)
n(n+5) is divisible by 6
for each
ノ
integer
Proof (ay induction)
P(O)= "o (o?+5) is divisible by 6"? 610 -0
nzo
Since
6.0= 0 V
P(K) > P(K+I): Let KE Z Ə
Assume
*0そオ
PCK) is true
"K (K?+5) is divisible by
that is,
So this mean that
6d - k(k²+5) for some
ivisibility
NTS: k+i(K+)+5) is divisible by 6
int gger
definition
d. by
of
(kt)((k1)*+5)= (kt1)(k*+2k +6)
= K3+3K?+ 8k t6
(k3+5k) +3K²+3k +6
k(k?+5) + 3k²+3K+6
Now,
by algebra
%3D
6d + 3k²+3K+6
by subsh tuton
= 6 (d + Klual) +) by algebra
2
integers closed
and products. Therefore ktl((K+1)*+5) is
divisibile by 6 by definition of divisibility.
Let e =
d + k(nt1)
le z since
2
undess sums](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fb341a54e-c99f-40a1-b702-440910997dde%2Fa15432d7-a4b5-4479-a4fc-8ffb7f93542d%2Fps2lk5f_processed.jpeg&w=3840&q=75)
Transcribed Image Text:15)
n(n+5) is divisible by 6
for each
ノ
integer
Proof (ay induction)
P(O)= "o (o?+5) is divisible by 6"? 610 -0
nzo
Since
6.0= 0 V
P(K) > P(K+I): Let KE Z Ə
Assume
*0そオ
PCK) is true
"K (K?+5) is divisible by
that is,
So this mean that
6d - k(k²+5) for some
ivisibility
NTS: k+i(K+)+5) is divisible by 6
int gger
definition
d. by
of
(kt)((k1)*+5)= (kt1)(k*+2k +6)
= K3+3K?+ 8k t6
(k3+5k) +3K²+3k +6
k(k?+5) + 3k²+3K+6
Now,
by algebra
%3D
6d + 3k²+3K+6
by subsh tuton
= 6 (d + Klual) +) by algebra
2
integers closed
and products. Therefore ktl((K+1)*+5) is
divisibile by 6 by definition of divisibility.
Let e =
d + k(nt1)
le z since
2
undess sums
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