Question

cho a=3+3^2+3^3+3^4+...+3^2013.CMR A chia het cho 39

Answer 1

a = (3+3^2+3^3)+(3^4+3^5+3^6)+.......+(3^2011+3^2012+3^2013)

   = 39+3^3.(3+3^2+3^3)+.....+3^2010.(3+3^2+3^3)

   = 39+3^3.39+......+3^2010.39

   = 39.(1+3^3+......+3^2010) chia hết cho 39

Tk mk nha

Answer 2

a = (3+3^2+3^3)+(3^4+3^5+3^6)+.......+(3^2011+3^2012+3^2013)

   = 39+3^3.(3+3^2+3^3)+.....+3^2010.(3+3^2+3^3)

   = 39+3^3.39+......+3^2010.39

   = 39.(1+3^3+......+3^2010) chia hết cho 39

 

Answer 3

 Phạm Tuấn Đạt đúng rồi