The data cannot be modeled by a linear equation....the rate of change is not constant. There's not an exact linear equation for that.
1) In this table, let's pick two points (1, 18) and (2,15) to find out the slope/ rate of change
2) Now, let's write the function and test it by plugging the slope and one of those points: (1, 18)
y=mx +b
18 = -3(1) + b
18 = -3 +b
18+3 = b
b= 21
y= -3x +21
3) Examining the function and the table, we can see that
x | y
1 18
2 15
4 9 This output does not match with the table
8 -3 This output does not match with the table
So, we can conclude that the data cannot be modeled by a linear equation....the rate of change is not constant
As we can see from the points on the table, they do not follow a precise line. In this case, the best thing would be a line of best fit to approximate those.