This is a linear function y=mx + b
If x = 0 then y=b, if A is the point where y intercepts y-axis, the coordinates of
A(0,b)
If you want to shift the graph up by 2 units, then you have to add 2 units to b
In our case original b=7, =so to shift it up, b becomes 7+2=9
and the new function will be y=2x + 9