SSC CHSL 15 Oct 2020 Shift 3 Paper

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Question : 65 of 100

Marks: +1, -0

If

x+y=15

and

x y=14

, then the value of

x-y

is

11
12
14
13

Solution:

Given,

x+y=15

and

x y=14

We know that,

(x+y)^{2}=x^{2}+2 x y+y^{2}

⇒

(15)^{2}=x^{2}+2 ×14+y^{2}

⇒

225=x^{2}+y^{2}+28

⇒

x^{2}+y^{2}=225-28=197

...(i)
Now, we know that,

(x-y)^{2}=x^{2}-2 x y+y^{2}

⇒

(x-y)^{2}=197-2 ×14

⇒

(x-y)^{2}=197-28=169

⇒

x-y=\√{169}=13

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