Question

Plz answer quickly with explanation.

Answer 1

Final Answer : ±4

Steps :
1)
${x}^{2} + \frac{1}{ {x}^{2} } = 18 \\ {(x - \frac{1}{x} \: ) }^{2} + 2 = 18 \\ = > {(x - \frac{1}{x} )}^{2} = 16 \\ = > (x - \frac{1}{x} ) = + 4or \: - 4$