Question

If a+b+c=6 and a²+b²+c²=20 find ab+bc+ac

Answer 1

(a+b+c)² = a²+b²+c²+ 2ab + 2bc + 2ca

6² = 20 + 2ab + 2bc + 2ca

36 -20 = 2(ab+bc+ca)
16/2 = ab + bc + ca

ab + bc+ca = 8

Answer 2

Answer:

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