Question

If a²+b²+c²=80and a+b+c=20 then find the value of ab+BC+ca

Answer 1

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Answer 2

We know
$(a + b + c){2} = a ^{2} + {b}^{2} + {c}^{2} + 2(ab +bc + ca)$
20 sq = 80 +2(ab +bc+ca)
=> 400-80/2 = ab+bc + ca
=>160= ab+ bc+ca