If a2 + b2 + c2 = 560 and ab + bc + ca =8, then a + b + c is Pick:
A) 4  B) 52  C) 16  D) 24  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 = 560 and ab + bc + ca = 8,   (a + b + c)^2 = 560 + 2(8)   = 576   = 24^2   therefore: a + b + c = 24   ANSWER:24
<result>D</result>
If a2 + b2 + c2 = 560 and ab + bc + ca =8, then a + b + c is