Answer:
68.965
Step-by-step explanation:
 
        
                    
             
        
        
        
The length of side c would be 8.
Step-by-step explanation:
Given that,
a = 4
b = 6
cosC = -1/4
If we are given two sides and angle, the law of Cosines can be used to find the third side:

By inserting the values in the formula, we get
 
 



c = 8.
Therefore, the length of side c would be 8.
 
        
             
        
        
        
(-1,-9) because if we substituted 1 into x y would be 9 and if we substituted 1/2 into x y would be 3 but if we substituted -1 into x y would be 1/9 so therefore that value is incorrect