Question

If a+b+c =6 and a²+b²+ c²=20, find ab+bc+ca.​

Answer 1

Answer:

9

Step-by-step explanation:

[(a+b+c)^2=a²+b²+ c²+2(ab+bc+ca]----Formula

=(6)^2=20+2(ab+bc+ca)

=36-20=2(ab+bc+ca)

18=2(ab+bc+ca)

18/2=ab+bc+ca

9=ab+bc+ca

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Answer 2

Answer:

8

Step-by-step explanation:

$(a+b+c)^{2}=a^2+b^2+c^2+2(ab+bc+ca)$

putting values from given question,

let  $ab+bc+ca$  be  $x$

therefore

       $6^{2} =20+2(x)$

       $36-20=2(x)$

       $16=2(x)$

       $x=8$  ---------(1)

from our assumption,

$ab+bc+ca=x$

from (1)

$ab+bc+ca=8$

hope it helps,

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