Question

guys please help me to solve ques. no. 5

Answer 1

hey your ans is here


_____

given

a2+b2+c2=20
a+b+c=0

to find

Ab+BC+ca
now apply

(a+b+c)2=a2+b2+c2+2(Ab+BC+ca)
(0)2=20+2(Ab+BC+ca)
-20/2=Ab+BC+ca
-10=Ab+BC+ca

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Answer 2

a^2+b^2+c^2=20
a+b+c=0
a^2+b^2+c^2 + 2(ab+bc+ca)=(a+b+c)^2
20-0=2(ab+bc+ca)
20/2=ab+bc+ca
ab+bc+ca=10