A line passes through (5 ,0 )(5,0) and (7 ,3 )(7,3). A second line passes through (3 ,6 )(3,6). What is one other point that the second line may pass through if it is parallel to the first line?

1 Answer
Mar 24, 2016

A point that makes Q_1Q_2Q1Q2 // P_1P_2P1P2
Q_2(0, 3/2)Q2(0,32)

Explanation:

Given:
1) Line pp given by points P_1(5,0) and P_2(7,3)P1(5,0)andP2(7,3), p => bar(P_1P_2)p¯¯¯¯¯¯¯¯P1P2
2) Lineqq given by points Q_1(5,0) and Q_2(x,y)Q1(5,0)andQ2(x,y), q => bar(Q_1Q_2)q¯¯¯¯¯¯¯¯¯Q1Q2
Required Q_2(x,y)Q2(x,y)?
We are going to use the following Definition and Principles:
a) Equation of line y_p=m_px+b_pyp=mpx+bp,
b) It's perpendicular line passing through Q_iQi and given by: y_(per)= -1/mx+b_(per)yper=1mx+bper
c) Equation of line y_q=m_qx+b_qyq=mqx+bq
d) Now given c) any point Q_2(x,y)Q2(x,y) on y_qyq will yield:
So let's get started:

color(red)(=>(a) y_p= m_px+b_p)(a)yp=mpx+bp
m_p=(3-0)/(7-5)=3/2mp=3075=32; y_p= 3/2x+b_pyp=32x+bp insert P_1(5,0)P1(5,0) and solve for b=-15/2b=152
y_p= 3/2x-15/2yp=32x152

color(blue)(=>(b) y_(per)= -1/mx+b_(per))(b)yper=1mx+bper
m_(per)= -1/m_p=-2/3mper=1mp=23
y_(per)= -2/3+b_(per)yper=23+bper insert Q_1(3,6)Q1(3,6) and solve for b_(per)=4bper=4
y_(per)= -2/3+4yper=23+4

color(green)(=>(c) y_(q)= m_qx+b_(q))(c)yq=mqx+bq
m_(q)= m_(P)=3/2mq=mP=32
y_(q)= 3/2+b_(q)yq=32+bq insert Q_1(3,6)Q1(3,6) and solve for b_(q)=3/2bq=32
y_(q)= 3/2x+3/2yq=32x+32

color(magenta)(=>(d) find Q_2(x,y) " using "y_(q)= 3/2x+3/2 (d)fdQ2(x,y) using yq=32x+32
Last pick any value for x and find y, you have your points:
Let's try x=0; y_q=3/2x=0;yq=32
#Q_2(0, 3/2)

To show this two lines are parallel find the vectors:
vec(P_1P_2)=vec(p)=>((7-5, 3-0) = 2i +3j+0k−−P1P2=p((75,30)=2i+3j+0k
vec(Q_1Q_2) = vec(q)=>((3-0, 6-3/2) = 3i +9/2j+0k−−Q1Q2=q((30,632)=3i+92j+0k
vec(P_1P_2)xxvec(Q_1Q_2) =det[(i,j,k),(2,3,0),(3,9/2,0)]
vec(P_1P_2)xxvec(Q_1Q_2) =k[2*9/3-9] = 0
This confirm that li p and q are parallel to one another and you are done.