Question

3. If a + b + c = 0 and a2+ b2 + c2 = 20, find ab + bc + ca.​

Answer 1

Answer:

a+b+c=0

a²+b²+c²=20

(a+b+c)²=a²+b²+c²+2ab+2bc+2ac

(a+b+c)²=a²+b²+c²+2(ab+bc+ac)

(0)²=20+2(ab+bc+ca)

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

-20=2(ab+bc+ca)

-10/2=ab+bc+ca

-5= ab + bc + ca

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