MCQ
Choose the correct answers from the given four option:
If $A$ and $B$ are two sets, then $\text{A} \cap (\text{A} \cup \text{B})$ equals.
  • $\text{A}$
  • B
    $\text{B}$
  • C
    $\phi$
  • D
    $\text{A}\cap\text{B}$

Answer

Correct option: A.
$\text{A}$
Given that: $\text{A}\cap(\text{A}\cup\text{B})$
Let $\text{x}\in\text{A}\cap(\text{A}\cup\text{B})$
$\Rightarrow \text{x}\in\text{A}$ and $\text{x}\in(\text{A}\cup\text{B})$
$\Rightarrow \text{x}\in\text{A}$ and $(\text{x}\in\text{A}$ or $\text{x}\in\text{B})$
$\Rightarrow (\text{x}\in\text{A}$ and $\text{x}\in\text{A})$ or $(\text{x}\in\text{A and x}\in\text{B})$
$\Rightarrow \text{x}\in\text{A}$ or $\text{x}\in(\text{A}\cap\text{B})$
$\Rightarrow \text{x}\in\text{A}$
Hence, the correct option is $(a).$

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