B i 2.à Cho tam gi¸c ABC ,A(3;-5), B(1;-3), C(2;-2).ViÕt PT tæng qu¸t :
a)c¸c c¹nh AB, AC, BC
b)§êng cao AH vµ Trung tuyÕn AM
c)§êng th¼ng qua A vµ song song víi BC
xÐt vÞ trÝ t¬ng ®èi b)
1 2
1 4
: 2 4 10 0; : ( )
2 2
x t
x y t R
y t
= −

∆ + − = ∆ ∈

= +

VÝ dô1: X¸c ®Þnh gãc gi÷a hai ®êng th¼ng trong c¸c trêng hîp sau:

( )
1 2
: 3 2 1 0; :
7 5
x t
x y t R
y t
=

∆ − + = ∆ ∈
