Question

calculați S=f(1)+f(2)+...+f(100) știind ca f(x)=x-2​

Answer 1

f(x)=x-2
f(1)=1-2= -1
f(2)=2-2=0
f(3)=3-2=1
f(4)=4-2=2
.
.
.
f(100)=100-2=98
Deci, astfel obținem o suma Gauss:
S=-1+0+1+2+…+98
S=1+2+…+98-1
S=98*99/2-1
S=9702/2-1
S=4851-1
S=4850