(((20點!!!急求救))求P的y坐標

用兩點式求ＡＢ的式：
得：４Ｙ＝６Ｘ－１８
代　Ｘ＝（－７／３）入上式
答：Ｙ＝－８．
努力

AB直線方程式 : (y-y1) / (x -x1) = (y2-y1) / (x2-x1)

(y-0) / (x-3) = [0-(-6)] /[3-(-1)]
y/(x-3) = 6 /4 = 3 /2
2y = 3x - 9
2y-3x+9=0

代入Px坐標 x = -7/3
2y-3(-7/3)+9 =0
2y+7+9 =0
2y = -16
y = -8

P的y坐標 = -8

Gradient of AB= 0-(-6) / 3-(-1) = 1.5
Y-intercept= -3*1.5 = -4.5
Formular of AB = Y=1.5x-4.5
Substitute x=-7/3 into the formular,
Y=1.5(-7/3)-4.5
Y=-8

therefor P's y-value is -8

Gradient of AB= 0-(-6) / 3-(-1) = 1.5
Y-intercept= -3*1.5 = -4.5
Formular of AB = Y=1.5x-4.5
Substitute x=-7/3 into the formular,
Y=1.5(-7/3)-4.5
Y=-8

therefor P's y-value is -8