Is the question multiple choice?
        
                    
             
        
        
        
Answer:
nah
Step-by-step explanation:
b
 
        
             
        
        
        
7/10 because you divide by 10
        
                    
             
        
        
        
a+b+c=0
[(a+b+c)^2=a^2+b^2+c^2+2ab+2ac+2bc]
[a^2+b^2+c^2+2ab+2ac+2bc=0]
[a^2+b^2+c^2=-(2ab+2ac+2bc)]
[a^2+b^2+c^2=-2(ab+ac+bc)] (i)
also
[a=-b-c]
[a^2=-ab-ac] (ii)
[-c=a+b]
[-bc=ab+b^2] (iii)
adding (ii) and (iii) ,we have
[a^2-bc=b^2-ac] (iv)
devide (i) by (iv)
[(a^2+b^2+c^2)/(a^2-bc)=(-2(ab+bc+ca))/(b^2-ac)]
        
             
        
        
        
Answer:
Angle ABC,
Step-by-step explanation:
Please give more detail to your question, this doesn't help at all...