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If a^2+b^2+c^2=21, and a + b + c = 7, th...

If `a^2+b^2+c^2=21`, and a + b + c = 7, then (ab + bc + ca) is equal to :
यदि`a^2+b^2+c^2=21` है तथा a +b + c = 7 है, तो (ab + bc + ca) का मान क्या होगा ?

A

12

B

28

C

14

D

8

Text Solution

Verified by Experts

The correct Answer is:
C
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MOTHERS-ALGEBRA -MULTIPLE CHOICE QUESTION
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  16. If 9a^2+4b^2+c^2+21= 4(3a + b - 2c), then the value of (9a + 4b - c) i...

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  17. If 135 sqrt5 x^3-2 sqrt2 y^3 div 3 sqrt5 x- sqrt2 y= Ax^2+By^2+sqrt10 ...

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