Question

Aratati ca numarul a= 2/3•5 + 3/5•8 + 4/8•12 apartine intervalului (0,2; 0,5).

Answer 1

2/3•5 + 3/5•8 + 4/8•12=
=2/15 + 3/40 + 1/24=
=(16+9+5)/120=
=30/120=
=1/4=0,25

0,2<0,25<0,5    deci a∈{0,2;0,5}