Question

2^n+2^n+1 +2^n+2 +2^n+3 este divizibil cu 15

Answer 1

2^n+2^(n+1)+2^(n+2)+2^(n+3) = 2^n +2^n*2+2^n*2^2+2^n*2^3 = 2^n( 1+2+2^2+2^3 ) =2^n ( 1+2+4+8 ) = 2^n*15 ( care este divizibil cu 15 ).