Question

(a) Find parametric equations for the line through (1, 4, 4) that is perpendicular to the plane x − y + 2z = 7. (Use the parameter t.)
(b) In what points does this line intersect the coordinate planes?

Answer 1

Answer:

$x=1+t\\y=4-t\\z=4+2t$

Step-by-step explanation:

A vector perpendicular to the plane ax+by+cz+d=0 is of the form $(a,b,c)$.

So, a vector perpendicular to the plane x − y + 2z = 7 is $(1,-1,2)$.

The parametric equations of a line through the point $(x_0,y_0,z_0)$ and parallel to the vector $(a,b,c)$ are as follows:

$x=x_0+at\\y=y_0+bt\\z=z_0+ct$

Put $(x_0,y_0,z_0)=(1,4,4)$ and $(a,b,c)=(1,-1,2)$

Therefore,

$x=1+t\\y=4-t\\z=4+2t$

xy-plane:

Put z = 0 ⇒ t = -2 ⇒x = - 1 , y = 6

So, at point (-1,6,0)

yz-plane:

Put x = 0 ⇒ t = -1 ⇒ y = 5, z =2

So, at point (0,5,2)

xz-plane:

Put y = 0 ⇒ t = 4 ⇒ x = 5, z = 12

So, at point (5,0,12)