Question

Se considera f:R->R, f(x)=4x-1. Calculati f(1)+f(2)+...+f(10).

Answer 1

f(1)=4*1-1=4-1=3
f(2)=4*2-1=8-1=7
f(3)=4*3-1=12-1=11
...............................
f(10)=4*10-1=40-1=39

S=3+7+11+...+39=  (3+39)*10/2=  42*5= 90