SSC CHSL 12 Oct 2020 Shift 3 Paper

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Question : 74 of 100

Marks: +1, -0

If

x^{2}+{1}/{x^{2}}=38

, then what is the value of

|x-{1}/{x}| ?

9
5
6
4

Solution:

We know that,

(a-b)^{2}=a^{2}+b^{2}-2 a b

∴

(x-{1}/{x})^{2}=x^{2}+{1}/{x^{2}}-2

⇒

(x-{1}/{x})^{2}=38-2

⇒

(x-{1}/{x})^{2}=36

⇒

(x-{1}/{x})=\√{36}

⇒

x-{1}/{x}=\±6

But

|x-{1}/{x}|=6

(only positive value)

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