Question

Find the remainder when 20^21 is divided by 1+400^7+20^7 ?​

Answer 1

Answer:

For n∈N∪{0} ,

f(n)=7n+7n+1+7n+2+7n+3

=7n(1+72)+7n+1(1+72)

=7n(1+7)(1+72)

is a multiple of 1+72=50. Hence the remainder when f(n) is divided by 25 is 0 for each n∈N∪{0}. ■

Answer 2

Answer:

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