Bài 7:
a: A={x\(\in\)N|x<7}
=>A={0;1;2;3;4;5;6}
b: B={x\(\in\)Z|-3<x<5}
=>B={-2;-1;0;1;2;3;4}
c: C={x|\(x=\dfrac{1}{2^k}\); k\(\in\)N; \(x< =\dfrac{1}{16}\)}
=>\(C=\left\{\dfrac{1}{32};\dfrac{1}{64};\dfrac{1}{128};...\right\}\)
d: D={x\(\in\)R|\(x^4-6x^2+8=0\)}
\(x^4-6x^2+8=0\)
=>\(\left(x^2-4\right)\left(x^2-2\right)=0\)
=>\(\left[{}\begin{matrix}x^2-4=0\\x^2-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x^2=4\\x^2=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\pm2\\x=\pm\sqrt{2}\end{matrix}\right.\)
Vậy: \(D=\left\{2;-2;\sqrt{2};-\sqrt{2}\right\}\)
e: E={x\(\in\)R|x là số chính phương nhỏ hơn 100}
=>E={0;1;4;9;16;25;36;49;64;81}
g: G={x\(\in\)N|x là bội chung của 12 và 20}
=>G={60;120;...}
\(A=\left\{0;1;2;3;4;5;6\right\}\)
\(B=\left\{-2;-1;0;1;2;3;4\right\}\)
\(C=\left\{\dfrac{1}{16};\dfrac{1}{32};\dfrac{1}{64};\dfrac{1}{128};...\right\}\)
D ko nhìn rõ đề
\(E=\left\{0;1;4;9;16;25;36;49;64;81\right\}\)
F ko rõ đề
\(G=\left\{60;120;180;240;300;...\right\}\)
