作业帮直线方程练习题
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直线方程练习题
直线方程练习题
直线方程练习题
B(x1,y1)
B is on l1
2x1+y1-6=0 (1)
|AB|=5
(x1-1)^2+(y1+1)^2=25 (2)
Sub (2) into (1)
(x1-1)^2+(7-2x1)^2=25
5(x1)^2-30x1+25=0
(x1)^2-6x1+5=0
(x1-5)(x1-1)=0
x1=1 or 5
case 1: when x1=1, y1=4
B(1,4)
equation of line AB
x-1 = 0
case2: when x1=5, y1=-4
B(5,-4)
equation of line AB
(y+4)/(x-5) = (-1+4)/(1-5)
= -3/4
4(y+4)=-3(x-5)
3x+4y+1=0