Question

Calculati sumele: (vedeti in poza)

Answer 1

Răspuns:

1-2+3-4+5-5+99-100=1

2-4-6-4-98-100=2

Answer 2

S=1-2+3-4+5-...+99-100

S=-1+(-1)+...+(-1)

S=(-1)•50

S=-50

S=-2-4-6-...-98-100

S=-(2+4+6+...+98+100)

S=-[2•(1+2+3+...+49+50)]

S=-[2•(50•51)/2]

S=-(50•51)

S=-2550