Răspuns :
Da-mi factor comun pe 5
[tex]S=5(1+2+3+...+20)[/tex]
Stim ca suma a n numere consecutive este
[tex]S_{n}=1+2+..+n=\frac{n*(n+1)}{2}[/tex]
Atunci
[tex]S=5*\frac{20*21}{2}=5*10*21=1050[/tex]
[tex]S=5(1+2+3+...+20)[/tex]
Stim ca suma a n numere consecutive este
[tex]S_{n}=1+2+..+n=\frac{n*(n+1)}{2}[/tex]
Atunci
[tex]S=5*\frac{20*21}{2}=5*10*21=1050[/tex]
imparti suma la 5
1+2+3+.......+20
20*(20+1)/2
20*21/2
420/2=210
210*5=1050(5+10+20+25+..........+100)
1+2+3+.......+20
20*(20+1)/2
20*21/2
420/2=210
210*5=1050(5+10+20+25+..........+100)
