Question

if a+b+c=5 & a^2b^2c^2=29 then the value of 3ab+3bc+3ca is

Answer 1

$a + b + c = 5 \\ {a}^{2} + {b}^{2} + {c}^{2} = 29 \\ now \\ {(a + b + c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2(ab + bc + ca) \\ = > {5}^{2} = 29 + 2(ab + bc + ca) \\ = > ab + bc + ca = - 2 \\ = > 3(ab + bc + ca) = - 6$
hope it helps