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Show that the points (i^-j^+3k^) and 3(i^+j^+k^) are equidistant from the plane r→⋅(5i^+2j^-7k^)+9 = 0 and lies on opposite side of it. - Mathematics

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Question

Show that the points `(hati - hatj + 3hatk)` and `3(hati + hatj + hatk)` are equidistant from the plane `vecr * (5hati + 2hatj - 7hatk) + 9` = 0 and lies on opposite side of it.

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Solution

To show that these given points `(hati - hatj + 3hatk)` and `3(hati + hatj + hatk)` are equidistant from the plane `vecr * (5hati + 2hatj - 7hatk) + 9` = 0

And are equidastant from the plane,

We have to prove that midpoint of these points lies on the plane.

Now midpoint of the given points is `2hati + hatj + 3hatk`

On substituting vector(r) by the mid point in plane, we get 

L.H.S. = `(2hati + hatj + 3hatk) * (5hati + 2hatj - 7hatk) + 9`

= 10 + 2 – 21 + 9

= 0

= R.H.S.

Hence, the two points lie on opposite sides of the plane are equidistant form the plane.

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Chapter 12: Introduction to Three Dimensional Geometry - Exercise [Page 237]

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NCERT Exemplar Mathematics [English] Class 11
Chapter 12 Introduction to Three Dimensional Geometry
Exercise | Q 25 | Page 237

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