THe general form of an equation of a luine can be written as follow:
y = mx + b
where m is the slpe of the line and b is the y-intercept
to calculate the slope m use the following formula:
m = (y2 - y1)((x2 - x1)
where (x1,y1) and (x2,y2) are any two points given on the table. Use:
(x1,y1) = (0,9)
(x2,y2) = (6,-21)
repalce the previous values to obtain m:
m = (-21 - 9)/(6 - 0)
m = -30/6
m = -5
next, to obtain b, use any point of the table (x,y), replace this point and the value of m, and solve for b, as follow:
use (x,y) = (0,9)
9 = -5(0) + b
9 = b
b = 9
Hence, m = -5 and b = 9. By replacing into the general expression for the linear equation, you obtain:
y = -5x + 9