A line passes through two points A(2, -3, -1) and B(8, -1, 2). The co-ordinate of a point on this line at a distance of 14 units from A are :
A. (14, 1, 5)
B. (86, 25,41)
C. (-10, -7, -7)
D. (-82, -31, -43)
E. (10, 7, 7)
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A and C only
eq. of line
$⇒\frac{x-x_1}{x_2-x_1}=\frac{y-y_1}{y_2-y_1}=\frac{z-z_1}{z_2-z_1}$
$⇒\frac{x-2}{8-2}=\frac{y+3}{-1+3}=\frac{z+1}{2+1}=λ$
$⇒x=6λ+2,y=2λ-3,z=3λ-1$
distance of this point from (A)
$(6λ+2-2)^2+(2λ-3+3)^2+(3λ-1+1)^2=14^2$
$36λ^2+4λ^2+9λ^2=14^2$
$49λ^2=14^2$
$λ^2=2^2⇒λ=±2$
so $P(x,y,z)$
(14, 1, 5) at x = 2 or (-10, -7, -7) at x = -2