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determina numarul natural x pentru care7·x+14·x+21·x+28·x+...+126·x≈7·9·19

Răspuns :

x•(7+14+21+28+...+126)=7•9•19
7+14+21+28+...+126=[(126+7)•18]:2=(133•18):2=2394:2=1197
x•1197=1197=>x=1197:1197
x=1
x•(7+14+21+28+...+126)=7•9•19
7+14+21+28+...+126=[(126+7)•18]:2=(133•18):2=2394:2=1197
x•1197=1197=>x=1197:1197
x=1