Question

 f (x)=4x-1. f(1) + f(2) +...f(10) = ?

Answer 1

f(1)=4*1-1=3;
f(2)=4*2-1=7
f(3)=4*3-1=11
f(4)=4*4-1=15
f(5)=4*5-1=19
f(6)=4*6-1=23
f(7)=4*7-1=27
f(8)=4*8-1=31
f(9)=4*9-1=35
f(10)=4*10-1=39 ....rezultatele merg din 4 in 4
acum faci adunarea 3+7+11+15+19+23+27+31+35+39=210