Question

aratati ca nr c= 2la puterea N x 3la puterea N+1 + 6la puterea N x 5 + 2la puterea N+1 x 3la puterea n+1. este divizibil cu 21

Answer 1

sper că te-am ajutat

Answer 2

C=2^n×3^(n+1)+6^n×5+2^(n+1)×3^(n+1)

=2^n×3^n×3+6^n×5+2^n×2×3^n×3

=3×6^n+5×6^n+6×6^n

=6^n(3+5+6)

=14×6^n

=2×7×6×6^(n-1)

=2×7×2×3×6^(n-1)

=21×4×6^(n-1) divizibil cu 21