Question

sa se afle media aritmetica a numerelor a si b daca intre multimile {a,12,b} si {2a+4,20,40} se stabileste o proportionalitate directa?

Answer 1

$\frac{a}{2a+4}=\frac{3}{5}=\frac{b}{40}$
De unde
5a=6a+12 =>a=-12
5b=120 =>b=24
$\frac{a+b}{2}=\frac{-12+24}{2}=6$