Question

If a^2 + b^2 + c^2 = 20 and a + b+ c = o find ab + bc + ca
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Answer 1

Step-by-step explanation:

a^2 + b^2 + c^2 = 20 and a + b+ c = 0

then ab + bc + ca = ??

expansion of (a+b+c)^2 = a^2+b^2+c^2+2bc+2ab+2ac

0 = 20 + 2(ab+bc+ca)

ab+bc+ca = -10

Answer 2

Answer:

-10

Step-by-step explanation:

We know the identity that

(a+b+c)^2 = (a^2+b^2+c^2)+2(ab+bc+ac)

As given in question, we can apply that_

(0)^2 = (20) + 2(ab+bc+ac)

ab+bc+ac= -20/2

= -10