Developing it says constructing equations from a table

The equation is y=2x+1.
to find b in y=mx+b you simply look for a point where x=0 which was (0,1) making the y-intercept or "b" equal to 1. to find the "m" or slope plug in any point for x and y. (9)=m(4)+1 is 2=m. so y=2x+1 is your answer.