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aflati nr.natural xdaca:3+6+9+.....+297=150x

Răspuns :

3(1+2+3+...+99)=150x
3·(1+99)·99:2=150x
300·99:2=150x
14850=150x
x=99

3+6+9+.....+297=150x      297÷3=99 de numere 
[(3+297)
×99]÷2
(300×99)÷2
29.700÷2=14.850
14.850=150x⇒⇒x=14.850÷150⇒⇒x=99