# parallel coordinate plane

• Dec 7th 2006, 06:50 PM
Schatzle06
parallel coordinate plane
What positive value of k would make the lines below parallel in the coordinate plane?
9x+ky=16
kx+4y=11

This problem is for extra points.
• Dec 7th 2006, 07:43 PM
ThePerfectHacker
Quote:

Originally Posted by Schatzle06
What positive value of k would make the lines below parallel in the coordinate plane?
9x+ky=16
kx+4y=11

This problem is for extra points.

( $k \not = 0$)

Express these in slope intercept form,
$ky=-9x+16$
$y=-\frac{9}{k}+\frac{16}{k}$

And,
$4y=-kx+11$
$y=-\frac{k}{4}x+\frac{11}{4}$

Two (non horizontal non vertical) lines are parralel if and only if there slopes are equal,
$-\frac{k}{4}=-\frac{9}{k}$
Remove the negative from both sides and cross multiply,
$k^2=36$
$k=\pm 6$