Incepem cu numaratorul:
2^n*7^(n+1)+14^(n+1)-14^n=
=7*(2^n)*(7^n) +2*(2^n)*7*(7^n) -(2^n)(7^n)=
=[(2^n)*(7^n)](7+14-1)=20*(2^n)*(7^n)
Apoi numaratorul:
2^(n+2)*7^n+14^n=
=4*(2^n)*(7^n) +(2^n)*(7^n)=(1+4)*(2^n)*(7^n)=5*(2^n)*(7^n)
Fractia devine:
[20*(2^n)*(7^n)]/5*(2^n)*(7^n)=20/5=4
