Question

f:R--->R ,f(x)=2x-3
sa se calculeze f(1)+f(2)+f(3)+............+f(100)
puteti sa mi explicati cum se face ?

Answer 1

f(1)=2*1-3=-1
f(2)=2*2-3=1
f(3)=2*3-3=3
....
f(100)=2*100-3=197

avem o progresie aritmetica cu ratia 2 si primul termen -1

$S_{n}= \frac{( a_{1}+ a_{n})*n }{2}$

$S_{100}= \frac{(-1+197)*100}{2}=196*50= 9800$