Question

daca x apartine N si o,(2x) +0,(3x) < 0,56 atunci x apartine multimi....?

Answer 1

banuiesc ca numerele 0,(2x) si 0,(3x) sunt cu bara deasupra, adica in baza 10
0,(2x)=2x/99 (2x cu bara deasupra)
0,(3x)=3x/99 (3x cu bara)
0,(2x)+0,(3x)=(50+2x)/99<0,56=56/100
2(25+x)/99<56/100 |:2
(25+x)/99<28/100
100(25+x)<99·28 |:4
25(25+x)<99·7
25+x<99·7/25
25+x<693/25
x<693/25-625/25
x<68/25
x<272/100
x<2,72
x∈{0,1,2}