Question

1. 2+4+6+...600=

2. 25+16+17+...+70

3. 5+6+7+...+81

4. 317+318+319+...+4000​

Answer 1

2+4+6+….+600
(Îl dam ca factor comun pe 2)
S=2•1+2•2+2•3+….+2•300
________________________
S=2•(1+2+3+…..+300)
S=2•[300•(300+1):2]
S=2•(300•301:2)
S=2•(90.300:2)
S=2•45.150
(Am aplicat metoda “suma lui Gauss”)





S=5+6+7….+81
S=80+79+78+….+5
________________
2S=85+85+85+…..+86
2S=85•86
2S=7310
S=7310:2
S=3655







S=317+318+319+……+4.000
S4000= 4.000•(4.000+1):2
S4000=4.000•4.001:2
S4000=160.040.000:2
S4000=8.002.000






Sper ca te-am ajutat! :D