Question

explain why 7 X 11 X 13 + 13 and 7 X 6 X 5 X 4 X 3 X 2 X 1 + 5 are composite numbers

Answer 1

Any composite no can be expressed as product of prime no
Since all its factors are prime no so the no will be composite no

Answer 2

Answer:

Given 7×11×13+13

=13×(7×11+1)=3×78

This number is multiple of two integers.Hence it has more than two factors.Hence it is a composite number.

similarly in

7×6×5×4×3 ×2×1+5

=5(7×6×4×3 ×2×1+1)=5×1009

This number is multiple of two integers.Hence it has more than two factors.Hence it is a composite number.