Question

the distance from the origin to image of (1,-1) with respect to the line X+y+5 =0
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Answer 1

Answer:

p(123), Plane :x−y+z=5

F is foot of perpendicular form P to plane and I is image,then PF=FI

∴ If (x,y,z)=(r+1,−r+2,r+3) are foot of perpendicular.

⇒(r+1)−(−r+2)+r+3=5⇒r=1

∴F=(2,1,4)

∴I=(3,0,5)

∴ distance of I from origin =

3

2

+0

2

+5

2

=

34