Question

Calculati Sumele c)S=5+10+15+...+100​

Answer 1

Răspuns:

1050

Explicație pas cu pas:

Suma S=5+10+15+...+100 are 100/5=20 de termeni

S=5+10+15+...+90+95+100

S=100+95+90+...+15+10+5

--------------------------------------

S+S=(5+100)+(10+95)+(15+90)+...(90+15)+(95+10)+(100+5)

2·S=105+105+105+...105+105+105

2·S=105·20

S=105·20/2=1050