Question

Prove that for any natural n the number 3^(n+4)−3^n is divisible by 16.

Answer 1

Answer:

Proved (See Explanation)

Step-by-step explanation:

Show that 3ⁿ⁺⁴ - 3ⁿ is divisible by 16.

This is done as follows

$\frac{3^{n+4} - 3^n}{16}$

From laws of indices;

aᵐ⁺ⁿ = aᵐ * aⁿ.

So, 3ⁿ⁺⁴ can be written as 3ⁿ * 3⁴.

$\frac{3^{n+4} - 3^n}{16}$ becomes

$\frac{3^n * 3^4 - 3^n}{16}$

Factorize

$\frac{3^n(3^4 - 1)}{16}$

$\frac{3^n(81 - 1)}{16}$

$\frac{3^n(80)}{16}$

3ⁿ * 5

5(3ⁿ)

The expression can not be further simplified.

However, we can conclude that when 3ⁿ⁺⁴ - 3ⁿ is divisible by 16, because 5(3ⁿ) is a natural whole number as long as n is a natural whole number.