If a2 + b2 + c2 = 213 and ab + bc + ca = 6, then a + b + c is	Choose the correct choice from the following choices:
A) 14	B) 20	C) 15	D) 32	E) 64
by formula ,   (a + b + c)^2= a^2 + b^2 + c^2 + 2(ab + bc + ca),   since, a^2 + b^2 + c^2 = 213 and ab + bc + ca = 6,   (a + b + c)^2 = 213 + 2(6)   = 225   = 15^2   therefore: a + b + c = 15   ANSWER:15
<result>C</result>
If a2 + b2 + c2 = 213 and ab + bc + ca = 6, then a + b + c is