Answer:
[tex]\frac{y_4-y_3}{x_4-x_3}\times \frac{y_2-y_1}{x_2-x_1}=-1[/tex]
Step-by-step explanation:
We know that,
If two line segments are perpendicular then the product of their slope is equal to -1,
Also, the slope of a line segment having the end points [tex](x_n,y_n)[/tex] and [tex](x_m,y_m)[/tex] is,
[tex]m=\frac{y_m-y_n}{x_m-x_n}[/tex]
So, the slope of line segment AB having end points [tex]A(x_1,y_1)[/tex] and [tex]B(x_2,y_2)[/tex] is,
[tex]m_1=\frac{y_2-y_1}{x_2-x_1}[/tex]
Similarly, the slope of line segment CD having end points [tex]C(x_3,y_3)[/tex] and [tex](x_4,y_4)[/tex] is,
[tex]m_2=\frac{y_4-y_3}{x_4-x_3}[/tex]
Hence, by the above property of perpendicular line segments ,
If AB and CD are perpendicular then,
[tex]m_1\times m_2=-1[/tex]
[tex]\implies \frac{y_4-y_3}{x_4-x_3}\times \frac{y_2-y_1}{x_2-x_1}=-1[/tex]
Third option is correct.