Question

Demonstrati ca nr A=2²³+2²²+2²¹ este divizibil cu 7. Va roggggggggggggggggggg ajutati-mã

Answer 1

[tex]A=2^{21}+2^{22}+2^{23} \\ Il~dam~factor~comun~pe~cel~mai~mic,~2^{21}: \\ A=2^{21}(1+2+2^2) \\ A=2^{21}*(1+2+4) \\ A=2^{21}*7 \\ Orice~numar~inmultit~cu~7~este~divizibil~cu~7~=> \\ =>7|A[/tex]