posted by Brandon on .
Find a linear function whose graph is the plane that intersects the xy-plane along the line y=2x+2 and contains the point (1,2,2).
a little vector analysis makes this relatively easy. Find two points B and C on the line. Let A=(1,2,2)
Form vectors AB and AC. These two vectors lie in the desired plane. Let n be the normal to the plane.
n = AB × AC
n•(v-A) = 0 is the desired plane.
So, pick any two points on the line, say B=(0,2,0) and C=(1,4,0)
AB = -i -2k
AC = 2j -2k
| i j k |
|-1 0 -2 |
| 0 2 -2 |
= 4i -2j + 2k
4i -2j + 2k • (x-1)i + (y-2)j + (z-2)k = 0
2x-y+z = 2
For a fuller explanation, see