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Ruslana9
a fost răspuns

10+20+30.....+800,13+26+39....+390,2+4+6+....200 >sa se afle suma

Răspuns :

Icecon2005
10+20+30.....+800=10×(1+2+3+......+80)=10×[80×81):2]=32400

 paranteza =- suma Gauss cu formula de calcul S= [n(n+1)]:2


13+26+39....+390=13(1+2+...+30)=13×[30×31):2]=13×465=6045

2+4+6+....200=2(1+2+.....+100)=2×[(100×101):2]=10100