Question

3^99-3^55 find the unit digit​

Answer 1

Answer:

7-7 = 0

The units digit is 0 as the unit digit of 3^99 as well as 3^55 is 7

Answer 2

3^1 ends with 3

3^2 ends with 9

3^3 ends with 7

3^4 ends with 1

3^5 ends with 3

So, the cyclicity of 3 is 4.

Divide 99 by 4. We get remainder 3.

So, 3^99 ends with 7.

Divide 55 by 4. We get remainder 3. So, 3^55 ends with 7.

So

3^99 - 3^55 ends with 7 - 7 = 0

So the unit digit is 0.