Question

if a^2+b^2+c^2= 80 and a+b+c=20 find ab+bc+ca​

Answer 1

Explanation:

(a+b+c)² = a²+b²+c²+2(ac+bc+ca)

(20)² = 80+2(ab+bc+ca)

400 = 80+ 2(ab+bc+ca)

400-80 =2(ab+bc+ca)

320 = 2(ab+bc+ca)

ab+bc+ca = 160 Answer.

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