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Cardinal Number

If A=x,x∈ℝ an...

Question

If $A = {x, x \in R and x^{2} - 4 x + 1 = 0}$ , then $n (A) =$

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Solution

$x^{2} - 4 x + 1 = 0$
$\Rightarrow x = \frac{4 \pm \sqrt{12}}{2} = 2 \pm \sqrt{3} \Rightarrow x = 2 - \sqrt{3}, 2 + \sqrt{3}$
$∴ n (A) = 2$

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Cardinal Number

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