Q.

If the length of the perpendicular drawn from the point (a,4,2), a>0 on the line x+12=y-33=z-1-1 is 26 units and Q(α1,α2,α3) is the image of the point P on this line, then a+∑i=13αi is equal to


Ans.

(8)

Given line X+12=Y-33=Z-1-1=λ

X=2λ-1,    Y=3λ+3,    Z=-λ+1

(2λ-1-a)2+(3λ-1)3+(-λ-1)(-1)=0

⇒4λ-2-2a+9λ-3+λ+1=0

14λ-4-2a=0⇒7λ-2-a=0

⇒(5λ-1)2+(3λ-1)2+(λ-1)2=24

35λ2-14λ-21=0⇒(λ-1)(35λ+21)=0

For, λ=1⇒a=5

Let (α1,α2,α3) be reflection point P

α1+5,    α2+4=12,    α3+2=0

α1=-3,    α2=8,    α3=-2

α1+α2+α3=8