Răspuns :
7 x 7³ x 7⁵ ...... x 7²⁹=
=7⁽¹⁺³⁺⁵⁺ ⁺²⁹⁾=7²²⁵
1+3+5+...+29=1+2+3+4+5+....+28+29-2-4-...-28=
=29*30/2-2(1+2+...+14)=
=29*15-2*14*15/2=
=29*15-14*15=
=15*(29-14)=15*15=15²=225
=7⁽¹⁺³⁺⁵⁺ ⁺²⁹⁾=7²²⁵
1+3+5+...+29=1+2+3+4+5+....+28+29-2-4-...-28=
=29*30/2-2(1+2+...+14)=
=29*15-2*14*15/2=
=29*15-14*15=
=15*(29-14)=15*15=15²=225