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Vaaaaaaaa roooooog!!!!!!! ​

Vaaaaaaaa Roooooog class=

Răspuns :

Explicație pas cu pas:

b) 10+20+30+...+1230= 10•(1+2+3...+123)= 10•( 123•124):2= 10•15252:2= 10•7626=76260

c) 7+14+21+...+315= 7•(1+2+3+...+45)=7•(45•46):2=7•2070:2=7•1035=7245