Question

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

Answer 1

${(a + b + c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2(ab + bc + ca)$
${(a + b + c)}^{2} = 20 + 2(8)$
${(a + b + c)}^{2} = 20 + 16 = 36$
$a + b + c = \sqrt{36} = 6$