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 Post subject: real analysis Posted: Sat Feb 10, 2018 5:15 pm

Joined: Mon Feb 05, 2018 4:22 am
Posts: 9
please solve it.

Let $A,B\subset\mathbb{R}$ nonempty. Define
\begin{align*}
A+B:&=\big\{x\in\mathbb{R}\,|\,\exists\,(a\in{A},b\in{B})\; {\text{such that}} \, x=a+b\big\}\\
&=\big\{a+b\,|\,a\in{A},b\in{B}\big\}\,.
\end{align*}
1. Let $A=[-1,2]=B$. What is $A+B$?
2. Let $A=B=\mathbb{N}$. What is $A+B$?
3. Let $A=B=\mathbb{Z}$. What is $A+B$?
4. Let $A=B=\mathbb{Q}$. What is $A+B$?
5. Let $A=B=\mathbb{R}\setminus\mathbb{Q}$. What is $A+B$?

 Last edited by admin on Sat Feb 10, 2018 6:53 pm, edited 1 time in total. Reason: Replace image file with LaTeX

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