Answer:
The value of k is -7
Explanation:
We are given the graph of f(x) and g(x). If g(x)=f(x)+k 
If we shift f(x) k unit vertical get g(x). 
If k>0 then shift up 
If k<0 then shift down. 
f(x) and g(x) are both parabola curve. 
First we find the vertex of f(x) and g(x) 
Vertex of f(x) = (3,1) 
Vertex of g(x) = (3,-6)
We can see change in y co-ordinate only. 
f(x) shift 7 unit down to get g(x) 
g(x)=f(x)-7
Therefore, The value of k is -7