Find the Best-Fit Line Associated with the Set of Points $( 3,9 )$

Essay

Find the best-fit line associated with the set of points.
​ $( 3,9 )$ , $( 5,16 )$ , $( 7,20 )$ , $( 9,0 )$ ​
Please enter your answer as an equation of line in the form $y = m x + b$ . Round m and b to the nearest hundredth if necessary.