Suppose a line is written as $\dfrac{x-x_1}{a}=\dfrac{y-y_1}{b}=\dfrac{z-z_1}{c}$. Which of the following is a valid direction vector of the line?
A$(x_1,y_1,z_1)$
B$(a,b,c)$
C$(x,y,z)$
D$(1,1,1)$
Answer & Solution
Correct answer: B. $(a,b,c)$
In symmetric form, the denominators give direction ratios of the line. So $(a,b,c)$ is a direction vector parallel to the line.
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