Question

if a^2+b^2+c^2=20 and a+b+c = 0 find ab+bc+ca​

Answer 1

Answer:

- 10

Step-by-step explanation:

Given that

a² + b² + c² = 20

(a + b + c) = 0

Then we have

(a + b + c)² = a² + b² + c² + 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

Therefore, ab + bc + ca = -10

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