Question

)If a+b+c=12 and a²+b²+c²=64,find the value of ab+bc+ac *

Answer 1

Step-by-step explanation:

$formula \\ {(a + b + c)}^{2} = {a }^{2} + {b}^{2} + {c}^{2} + 2(ab + bc + ca) \\ \\ given \: \\ a + b + c = 12 \\ {a}^{2} + {b}^{2} + {c}^{2} = 64 \\ \\ {(12)}^{2} = 64 + 2(ab + bc + ca) \\ 144 - 64 = 2(ab + bc + ca) \\ ab + bc + ca = \frac{80}{2} = 40$

hope it helps...