Show that the points ^i−^j+3^k and 3(^i+^j+^k) are equidistant from the plane →r.(5^i+2^j−7^k)+9=0 and lies on opposite side of it.
To show that these given points ^i−^j+3^k and 3(^i+^j+^k) are equidistant from the plane →r.(5^i+2^j−7^k)+9=0,we first find out the mid-point of the points which is 2^i+^j+3^k.
On substituting →r by the mid-point in plane,we get
LHS=(2^i+^j+3^k).(5^i+2^j−7^k)+9
=10+2-21+9=0
=RHS
Hence,the two points lie on opposite sides of the plane are equidistant from the plane.