Answer:
Graph 4
Explanation:
Allow me to revise your question: 
Which graph represents f(x)=−2
 
 
As we can see, the function has a degree of 3, so the two parabolic lines in graph 1 and 3 are not correct because they presents for the functions has has a degree of 2. 
Then we have graph 2 and 4 left. 
As we can see the coefficient "a= -2" functions to make the graph reflect via the x-axis. So graph 4 is the correct one that represents f(x)=−2
