Question

A={x ∈ lui N| x este cifra impara} B={x ∈ lui N| 2x-1 < 5} C={x ∈ N| 2x²+1<19}

Enumerati elementele multimilor A,B,C

Answer 1

A={x ∈ lui N| x este cifra impara}⇒A={1,3,5,7,9,11,13,15...n+1}

B={x ∈ lui N| 2x-1 < 5}
2x-1 < 5⇒2x≤6⇒x≤3⇒B={0,1,2,3}

C={x ∈ N| 2x²+1<19}
 2x²+1<19⇒2x²≤20⇒x²≤10⇒x≤√10⇒x≤3,16

C={0,1,2,3}