_{x}+ 3a

_{y}+ 2a

_{z}

B = -a

_{x}+ 4a

_{y}+ 6a

_{z}

C = 8a

_{x}+ 2a

_{y}

Find the value of m and n such that mA + nB + C is parallel to y-axis.

My problem is I did not know how to determine the m and n value because I did not know what method can use to solve for mA + nB + C parallel to y axis. Does it means that the vector line of mA + nB + C must be a straight line parallel to y axis?

mA + nB + C

= (5m - n + 8)a

_{x}+ (3m + 4n + 2)a

_{y}+ (2m + 6n)a

_{z}

To use dot product means that (mA + nB + C) dot (??) = 1

cross product means that (mA + nB + C) cross (??) = 0

I dunno the ?? is stand for what.... can someone pls help me?