Răspuns:
Explicație pas cu pas:
b)1+2+3+....+500=500×501:2=125250
c)1+97+2+999+3+198=(1+999)+(2+198)+(3+97)= 1000+200+100=1300
e)2+4+6+..+600=2×(1+2+3+...300) = 2×(300×301:2)= 90300
f)15+16+17+...+70=(1+2+3+...+70)-(1+2+3+..+14)= 70×71:2-14×15:2= 2485-105=2780
g)5+6+7+...+81=(1+2+3+...+81)-(1+2+3+4+5)=(81×82:2)-(5×6:2)=3321-15=3306
