Question

Which of the following has no solution?

Answer 1

A)

$\{x\,|\,x \leq 1\}\, \cap \,\{x\,|\,x \geq 1\}=(-\infty;1]\,\cap\,[1,\infty)=\{1\}$

b)

$\{x\,|\,x \ \textless \ 1\}\, \cap \,\{x\,|\,x \ \textgreater \ 1\}=(-\infty;1)\,\cap\,(1,\infty)=\boxed{\emptyset}$

c)

$\{x\,|\,x \leq 1\}\, \cup \,\{x\,|\,x \geq 1\}=(-\infty;1]\,\cup\,[1,\infty)=\mathbb{R}$

Answer b)