#### Answer

(a) A direction vector is $(4,2,3)$
(b) $(x,y,z) = (-1,2,4)+n(4,2,3)$

#### Work Step by Step

(a) We can find a direction vector:
$P_2-P_1 = (3,4,7) - (-1,2,4) = (4,2,3)$
A direction vector is $(4,2,3)$
(b) We can find an equation for this line:
$(x,y,z) = (-1,2,4)+n(4,2,3)$, where $n$ is a real number