What does this all means? Help!

Here's the graph :  https://www.desmos.com/calculator/gvm2oy7mhe

a) Domain = [ 0, infinity )

b) Range =  [ 0, infinity )

c) We cannot take the square root of a negative  (it is not a real number)

d) We can only get 0 or a positive number out of a positive root

e)  Avg rate of change   =  [ √ 16 - √ 1 ] / [ 16 - 1 ]  = [ 4  - 1 ] / 15   =  3/15    = 1/5 

f)   the function is  g(x) =    √ ( x + a)  + b