Question

5.Calculati suma numerelor naturale pare de forma 2xy barat

 Va rog!!! Este o urgenta!!!!!!!!!!!!!

Answer 1

2xy numar par
x={0,1,2,3,4,5,6,7,8,9}   10 cifre
y={0,2,4,6,8}                  5 cifre
nr sunt 10*5=50
200+202+204+206+208+210+212+214+216+218+220+222+224+226+228+230+
+232+234+236+238+240+242+244+246+248+250+252+254+256+258+260+262+
+264+266+268+270+272+274+276+278+280+282+284+286+288+290+292+294+
+296+298 =
=200*50+2(1+2+3+....+49)=200*50+2*49(49+1)/2=
=10000+49*50=10000+2450=12450