Question

a+b+c=5;a^2+b^2+c^2=2019 then ab+bc+cd=?​

Answer 1

Answer:

sorry friend it is too big to answer because of the a^2+b^2+c^2=2019. But I knew the formula a square + b square + c square +2(ab+bc+ca)

Answer 2

Answer:

Given,

a+b+c=5

(a+b+c)^2=5^2

a^2+b^2+c^2+2ab+2bc+2ca=25

2019+2(ab+bc+ca)=25

2(ab+bc+ca)=25-2019

ab+bc+ca=-1994/2

ab+bc+ca=-997