Question

Fie f:R-R f(x)=3x+5
a)Determinati a ∈R a.i. M(a,8)∈Gf
b) Calculati f(1)+f(2)+...+f(10)

Answer 1

Răspuns

1

215

Explicație pas cu pas:

3*a+5=8

a=1

3*1+5+3*2+5+...+3*10+5=3(1+2+...+10)+ 5+5+..+5 (de 10 ori)=

3*10*11/2+80=3*55+50=165+50=215

altfel

3*1+5=8 cel mai mic

3*10+5=35 cel mai mare

suma gauss...10 nuimere, 10/2 perechi de numere

(35+8)*10/2=430/2=215