斜率

点A(x1,y1) 点B(x2,y2)

k代表斜率,b为常数

     y1 - y2
k = —————————
     x1 - x2

y1 = k * x1 + b

y2 = k * x2 + b

y2 = k * x2 + ( y1 - k * x1 )

y1 = k * x1 + ( y2 - k * x2 )

若
点A(65,75) 点B(20,20)

     75-20
k = ——————— = 1.22
     65-20

y2 = 1.22 * 65 + (20 - 1.22 * 20)

y2 = 79.3 - 4.4 = 74.9

参考上述，已知斜率可推导y2，已知y2也可反推斜率