Question

if a^2+b^2+c^2=16and ab+bc+ca=10 find the value of a+b+c

Answer 1

${(a + b + c)}^{2} \\ = {a}^{2} + {b}^{2} + { c}^{2} + 2(ab + bc + ca) \\ = 16 + 2 \times 10 \\ = 16 + 20 \\ = 36 \\ a + b + c = \sqrt{36} \\ = + 6 \: or \: - 6$