If $ a^2 + b^2 + c^2 = 6.25 $ and (ab + bc + ca) = 0.52, what is the value of (a + b + c), if ( a +b + c ) < 0 ?

-2.7

If $ a^2 + b^2 + c^2 = 6.25 $ 

(ab + bc + ca) = 0.52

what is the value of (a + b + c)

(a + b + c)² = $ a^2 + b^2 + c^2$ + 2(ab + bc + ca)

(a + b + c)² = 6.25 + 2(0.52)

(a + b + c)² = 6.25 + 1.04

(a + b + c)² = 7.29

(a + b + c) = -2.7