Sainik School Entrance Exam 2020 Solved Paper

Question : 23 of 150

Marks: +1, -0

a+b+c=9

and

a b+b c+c a=23

, then the value of

a^2+b^2+c^2

equals to

Solution:

(a) From the question,

a+b+c=9

and

a b+b c+c a=23

From the identity

(a+b+c)^2=a^2+b^2+c^2+2(a b+b c+a c)

⇒9^2=a^2+b^2+c^2+2(23)

⇒81=a^2+b^2+c^2+46

⇒a^2+b^2+c^2=81-46=35

So,

a^2+b^2+c^2=35.

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