Create a table for the function y = x2 + 7x + y for y values from -7 to 0.
This seems to be a strange question because: y = x2 + 7x + y
subtracting y from both sides: 0 = x2 + 7x
and the y-term disappears!
So, solving for x: 0 = x(x + 7)
this means that either x = 0 or x = -7.
Thus, for every y-value, x has two possible values, either 0 or -7.