Question

f(x) = 2+x
sa se caulculeze f(1)+f(2)+...+f(20) = ? ajutor va rog

Answer 1

F(1)=3, f(2)=4, f(3)=5: se observa progresie aritmetica. Primul termen , a1=3, ratia r=1. S20=(a1+a20)20/2. A20=a1+19r=3+19=22. S20=(3+22)*10=250.