Răspuns :
Răspuns:
A) 10+20+30+...+200
Nr de termeni: (200-10):10+1
190:10+1=20
S= (10+200)*20/2= 210*20 supra 2=2100
B) 5+10+15+20+...+125
Nr de termeni: (125-5):5+1=25
S= (5+125)*25/2=130*25/2=1625
Răspuns:
10(1+2+3+...+20)= 10(1+20)*20/2=21*100=2100 ; B)
Explicație pas cu pas:
5(1+2+3+...+25)=(5+125)*25/2=65*25=1625