Hedwigeeeee
Badges: 18
Rep:
?
#1
Report Thread starter 3 weeks ago
#1
may I ask what does n-r+1 mean and why n(n-1)...(n-r+1)/r! equals to n!/(n-r)!r!
Attached files
Last edited by Hedwigeeeee; 3 weeks ago
0
reply
DreamingBoy
Badges: 7
Rep:
?
#2
Report 3 weeks ago
#2
it means the first expression on the left is equal to the second one
n!/(n-r)! cancel each term out to give n(n-1)...(n-r+1)

e.g
n=3,r=1
3!/(3-1)!=3*2*1/2*1=3=n*...*(n-r+1)=3 (n=n-r+1=3)
1
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Who is winning Euro 2020

France (110)
27.85%
England (135)
34.18%
Belgium (30)
7.59%
Germany (41)
10.38%
Spain (8)
2.03%
Italy (34)
8.61%
Netherlands (13)
3.29%
Other (Tell us who) (24)
6.08%

Watched Threads

View All
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise