If a2 + b2 + c2 = 390 and ab + bc + ca = 5, then a + b + c is Pick
A) 19
B) 20
C) 25
D) 30
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 = 390 and ab + bc + ca = 5,   (a + b + c)^2 = 390 + 2(5)   = 400   = 20^2   therefore: a + b + c = 20   ANSWER:20
<result>B</result>
If a2 + b2 + c2 = 390 and ab + bc + ca = 5, then a + b + c is