Question

f:R->R ,f (x)=8x-7
Calculati S=f(1)+f (2)+...+f (100)

Answer 1

suma de 100 termeni 
f(1) = 8 ·1 - 7 
f(2)  = 8 · 2 - 7 
..................
f(100) = 8 ·100 - 7 
-----------------------------------
suma = 8 ·( 1 +2 +.. + 100 )  - 7 ·100 = 
 = 8 ·( 1 +100 ) ·100 /2   - 700 
 = 4 ·101 ·100 - 700 =100 · ( 4·101  - 7 ) =100 · (404 - 7 ) = 397· 100