Question

[Phạm Tất Đạt]

A =\(\left\{x\in N\backslash\left(2x-x^2\right)\left(2x^2-3x-2\right)=0\right\}\)

B =\(\left\{n\in N^+\backslash3x< n< 30\right\}\)

Xét A

\(\left(2x-x^2\right)\left(2x^2-3x-2\right)=0\)

=> \(\left[{}\begin{matrix}\left(2x-x^2\right)=0=>x=2;x=0\\\\\left(2x^2-3x-2\right)=0=>x=2;x=-\frac{1}{2}\end{matrix}\right.\)

Vì \(x\in N\) => \(A=\left\{2\right\}\)

Xét B

\(3x< n^2< 30\)

<=> \(6< n^2< 30\)

<=> \(\sqrt{6}< n< \sqrt{30}\)

=>\(\left[\sqrt{6};\sqrt{30}\right]\)

Vì \(B\in N^+\) => \(B=\left[3;5\right]\)

\(A\cap B=\varnothing\)