If the distance between the points (7,1,-3) and `(4,5,lambda)` is 13 units, then what is one of the value of `lambda`?

Options

A. 20
B. 10
C. 9
D. 8

Answer

C

Explanation

We have,
`13=sqrt((4-7)^2+(5-1)^2+(lambda+3)^2)`
`169+9+16+lambda^2+9+6lambda`
`rArr lambda^2+6lambda-135=0`
`rArr lambda^2+15lambda-9lambda-135=0`
`rArr lambda(lambda+15)-9(lambda+15)=0`
`rArr (lambda+15)(lambda-9)=0`
`rArr lambda=-15or lambda=9`