Question

Prove that (n^3-n) is divisible by 6

Answer 1

Answer:

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Step-by-step explanation:

This can be solved using mathematical induction

Let us say f(n)=n^3-n

Now start with n=0 ,f(0)=0^3-0=0 is divisible by 6

n=1, f(1)=1^3-1=0 is divisible by 6

n=2, f(2)=2^3-2=6 is divisible by 6

n=3,f(3)=3^3-3=27-3=24 is divisoble by 6

So n^3-n is divisible by 6 is true for all n

Now let us suppose n=k

f(k)=k^3-k is divisible by 6

Now let us assumw n=k+1

f(k+1)=(k+1)^3-(k+1)

=k^3+k^2+k+1-k-1

=k^3-k-1+k^2+k+1

=is divisible by 6

So by using mathematical induction we prove that n^3-n is divisible by 6

Answer 2

Step-by-step explanation:

▶ n³ - n = n (n² - 1) = n (n - 1) (n + 1)

Whenever a number is divided by 3, the remainder obtained is either 0 or 1 or 2.

∴ n = 3p or 3p + 1 or 3p + 2, where p is some integer.

If n = 3p, then n is divisible by 3.

If n = 3p + 1, then n – 1 = 3p + 1 –1 = 3p is divisible by 3.

If n = 3p + 2, then n + 1 = 3p + 2 + 1 = 3p + 3 = 3(p + 1) is divisible by 3.

So, we can say that one of the numbers among n, n – 1 and n + 1 is always divisible by 3.

⇒ n (n – 1) (n + 1) is divisible by 3.

Similarly, whenever a number is divided 2, the remainder obtained is 0 or 1.

∴ n = 2q or 2q + 1, where q is some integer.

If n = 2q, then n is divisible by 2.

If n = 2q + 1, then n – 1 = 2q + 1 – 1 = 2q is divisible by 2 and n + 1 = 2q + 1 + 1 = 2q + 2 = 2 (q + 1) is divisible by 2.

So, we can say that one of the numbers among n, n – 1 and n + 1 is always divisible by 2.

⇒ n (n – 1) (n + 1) is divisible by 2.

Since, n (n – 1) (n + 1) is divisible by 2 and 3.

∴ n ( n - 1 ) ( n + 1 ) = n³ - n is divisible by 6.( If a number is divisible by both 2 and 3 , then it is divisible by 6)

✔✔ Hence, it is solved ✅✅.