Saturday

September 5, 2015
Posted by **J** on Saturday, May 5, 2012 at 12:28pm.

- Calculus -
**Reiny**, Saturday, May 5, 2012 at 4:04pmI think you posted this before, and probably got no response.

You asked for "the" line parallel to the plane

2x+6y+4z = 1.

There is no unique line.

Think of the floor of your kitchen as 2x+6y+4z = 1 and you have a table whose top is parallel to the floor and contains the point (3,2,1).

Laying down a ruler would be a line parallel to the plane and passing through the point.

How many such positions could you choose ?

a normal to your given plane is (2,6,4) or (1,3,2)

so any vector whose dot product with the above normal would be parallel to the plane

e.g. (-5,1,1)∙(1,3,2) = -5+2+3 = 0

and (1,-1,1)∙(1,2,3) = 1-3+2 = 0 are just two such vectors

let's take (-5,1,1)

so the equation of one such line is

x = 3 -5t

y = 2 + t

z = 1 + t

- Calculus -
**J**, Sunday, May 6, 2012 at 1:34amthank you :)