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48 Chapter Onł

Figure 1.11 Point-slope plot of the equation y 104
3(x 72).

P (x ,y )
p
p
Q (x ,y )
q
q
Then the slope m of the line is given by the either of the follow-
ing formulas:

m (y y )/(x x )
p
q
p
q
m (y y )/(x x )
p
p
q
q
The point-slope equation of the line can be determined based on
the known coordinateð of P or Q. Therefore, either of the follow-
ing formulas represent the line:
y y m(x x )
p
p
y y m(x x )
q
q