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35+20+24+28+...+156 va rog mult!

Răspuns :

Deci: 35+20+24+28+...+156=156+157:2= 156,rest 5

35+20+24+28+...+156=
=35+4(5+6+7+...+39)=
=35+4(1+2+3+4+5+6+7+...+39-1-2-3-4)=
=35+4(39*40/2-10)=
=35+4(780-10)=
=35+4×770=
=35×(1+4×22)=
=35×(1+88)=
=35×89=3115