Răspuns: [tex]\red{\boxed{\bf x = 4}}[/tex]
Explicație pas cu pas:
[tex]\bf \{3,~ x+ 5 \} ~si~ \{1,~ 2x + 1\}[/tex]
[tex]\bf x+5 = 2x+1[/tex]
[tex]\bf x+5-1 = 2x[/tex]
[tex]\bf 2x=x+4[/tex]
[tex]\bf 2x-x=4[/tex]
[tex]\red{\boxed{\bf x = 4}}[/tex]
[tex]\bf \{3,~ 4 + 5 \} ~si~ \{1,~ 2\cdot4 + 1\}[/tex]
[tex]\bf \{3,~ 9 \} ~\cap~ \{1,~ 9\} = \red{\{9\}}[/tex]
