Question

scoateti factorul comun:
S3=5+10+15+...+500

Answer 1

s = 5 · ( 1 + 2 +3 +.. + 100 ) 
= 5 · ( 1 + 100 ) · 100 / 2 
= 5 · 101 · 50 
 = 25250

Answer 2

[tex]S _{3}=5+10+15+...+500 S _{3}=5(1+2+3+...+100) S _{3} =5(100*101:2) S_{3} =5(50*101) S _{3} =5*5050 S _{3} =25250[/tex]

Formula pentru suma lui Gauss:$n*(n+1):2$