If a+b+c= 10, a^2+b^2 +c^ =40 find ab+bc+ca

1.	If a+b+c= 10, a^2+b^2 +c^ =40 find ab+bc+ca
Answer» Now, by using the identity a+b+c)^2 = a^2+b^2+c^2+2 (ab+bc+ca) Now here , we have given value of a+b+c = 10 and a^2+b^2+c^2 = 40 So , putting these values in identity we get (10)^2= 40 +2 ( ab +bc+ca) 100 = 40+2 ( ab+ bc+ ca ) 2 ( ab+ bc+ ca ) = 100-40 :) ab+ bc+ ca = 60 ÷2 :) = 30 How it is possible

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