Question

aratati ca a=2 la puterea 25 +2 la puterea 26 +2 la puterea 27 +2 la puterea 28 divizibil cu 15

Answer 1

[tex]a=2^{25}+2^{26}+2^{27}+2^{28}\\ a=2^{25}(1+2+2^2+2^3)\\ a=2^{25}(1+2+4+8)\\ a=2^{25}\cdot 15\ \vdots\ 15[/tex]