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a fost răspuns

a+b=10, a+b+2(a+b)+...+100(a+b)

Răspuns :

1(a+b)+2(a+b)+....+100(a+b)= 10+2*10+3*10+....+100*10= 10*(1+2+3+...+100)= 10* 100*101/2 = 500*101=50500
10+2*10+3*10+...+100*10=

=10x(1+2+...+100)=10x[(100x101)/2]=10x5050=50500

Am folosit: 1+2+...+n=n(n+1)/2

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