Question

if a^2+b^2+c^2=30and a+b+c=10 then find the value of ab+bc+ca​

Answer 1

Ans:- (a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca

= (10)^2 = 30 + 2(ab+ bc+ ca)

= 100 - 30 = 2(ab+ bc + ca)

= (ab + bc + ca) = 35.

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