Find the distance of the point `hati + 2hatj - hatk` from the plane `barr*(hati - 2hatj + 4hatk) = 10`.

Explanation

The distance of the point A`(bara)` from the plane `barr*barn = p` is given by
`d=(|bara*barn-p|)/(|barn|)`
Here, `bara=hati+2hatj-hatk, barn=hati-2hatj+4hatk` and p = 10.
`therefore bara*barn=(hati+2hatj-hatk)*(hati-2hatj+4hatk)`
` = 1(1) + 2(-2) + (-1)(4)`
` = 1-4-4 = -7`
and `|barn|=sqrt(1^(2)+(-2)^(2)+4^(2))=sqrt(1+4+16)=sqrt(21)`
` therefore` required distance ` = (|-7-10|)/(sqrt(21)) = (17)/(sqrt(21))` units.