Show that the line through the points `(4, 7, 8), (2, 3, 4)`is parallel to the line through the points `( 1, 2, 1)`,`(1, 2, 5)`.

Explanation

Direction ratios of the line passing through the points `(4,7,8),(2,3,4)` are
`a_(1),b_(1),c_(1) = 2-4,3-7,4-8`
`= - 2,-4,-4`
Direction of the line passing through the points `(-1,-2,1),(1,2,5)`
`a_(2),b_(2),c_(2)=1+1,2+2,5-1=2,4,4`
Now, `(a_(1))/(a_(2)) = (b_(1))/(b_(2)) = (c_(1))/(c_(2))`
Therefore, two lines are parallel .