Question

f(x)=3x-2 sa se calculeze f(1)+f(2)+...+f(5)​

Answer 1

Răspuns:

f(x) = 3x - 2

f(1) = 3 * 1 - 2 = 3-2 = 1

f(2) = 3* 2 - 2 = 6-2 = 4

f(3) = 3 * 3 - 2 = 9-2 = 7

f(4) = 3 * 4 - 2 = 12-2 = 10

f(5) = 3 * 5 - 2 = 15 - 2 = 13

f(1)+f(2)+...+f(5) = 1 + 4 + 7 + 10 + 13 = 35 ☑️

Answer 2

$\it f(x)=3x-2\\ \\ f(1)+f(2)+f(3)+f(4)+f(5) = 1+4+7+10+13=\dfrac{(1+13)\cdot5}{2}=35$

Termenii sumei sunt termeni ai unei progresii aritmetice cu rația 3.