Show that the product of k consecutive natural numbers is divisible by k!
Answers
Answer:
The product of k consecutive integers is divisible by k! , in particular by k (provided k≥1 ).
Step by step explanation:
If m is the first of the consecutive integers, set n=m+k−1 , so
m(m+1)…(m+k−1)=n(n−1)…(n−k+1)
so
(nk)=n(n−1)…(n−k+1)k!
is the number of ways to choose k elements from n , which is obviously an integer.
The product of k consecutive natural numbers. Hence, the product of k consecutive natural numbers is divisible by k!.
Let's consider k consecutive natural numbers starting from n, then the product of these numbers is:
n(n+1)(n+2)...(n+k-1)
Now, we need to prove that this product is divisible by k!.
We know that k! can be written as:
k! = k(k-1)(k-2)...(2)(1)
We can see that k! contains all the factors that appear in the product of k consecutive natural numbers.
To prove that the product of k consecutive natural numbers is divisible by k!, we need to show that each factor in k! appears at least once in the product of k consecutive natural numbers.
Let's consider the ith factor in k! which is (k-i+1). This factor appears in the product of k consecutive natural numbers in the following way:
(n+i-1)(n+i-2)...(n+1)n
We can see that the first factor in this expression is (n+i-1) which is the same as (k-i+1). Similarly, the second factor is (n+i-2) which is the same as (k-i+2). This pattern continues until the last factor which is n, and it is the same as k.
Therefore, each factor in k! appears at least once in the product of k consecutive natural numbers. Hence, the product of k consecutive natural numbers is divisible by k!.
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