Question

if a+b+c=8 and a^2+b^2+c^2=20 then find the value of ab+bc+ca​

Answer 1

Answer:

a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca

(a+ b + c)2 = a2 + b2 + c2+ 2 (ab + bc + ca)

(20)2 = 90 + 2 (ab + bc + ca)

400 - 90 = 2 (ab + bc + ca)

ab + bc + ca = 155