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If A2 + B2 + C2 = 20 and a + B + C = 0, Find Ab + Bc + Ca. - Mathematics

Answer in Brief

If a2 + b2 + c2 = 20 and a + b + c = 0, find ab + bc + ca.

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Solution

Recall the formula

 `(a+b+c)^2 = a^+b^2 +c^2 +2(ab +bc +ca)`

Given that

`a^2 +b^2 +c^2 = 20`

`(a+b+c) = 0`

Then we have

                 `(a+b+c)^2 = a^2 +b^2 +c^2 +2 (ab +bc + ca)`

                                `(0)^2 = 20 +2(ab +bc + ca)`

  ` 20+2(ab +bc + ca) = 0`

            `2(ab + bc + ca) = -20`

               `(ab +bc + ca) = -10`

  Is there an error in this question or solution?
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APPEARS IN

RD Sharma Mathematics for Class 9
Chapter 5 Factorisation of Algebraic Expressions
Q 2 | Page 24
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