Question

calculati 1.(8)+2,(7)+3,(6)+......+7,(2)+8,(1)

Answer 1

Răspuns:

Explicație pas cu pas:

poza

Answer 2

S = 1,(8)+2,(7)+3,(6)+...+7,(2)+8,(1)  

S = 8,(1)+7,(2)+6,(3)+...+2,(7)+1,(8)

2S = [1,(8)+8,(1)]+[2,(7)+7,(2)]+[3,(6)+6,(3)]+...+[7,(2)+2,(7)]+[8,(1)+1,(8)]

2S = 9,(9)+9,(9)+9,(9)+...+9,(9)+9,(9)  {de 8 ori}

2S = 10+10+10+...+10+10 {de 8 ori}

2S = 10×8

2S = 80

S = 80/2

=> S = 40