In the system of equations above, a is a constant. For - 3x + y = 6
ax + 2y = 4
What is the
which of the following values of a does the system
have no solution?
A) -6
B) -3
C)3
D)6
( I know the answer I just don’t know how to solve it)

A

Explanation:

to have no soluion, two lines are parallel, which means their slopes are same, but different y-intercept. (if two line have same slope and same y-intercepts, they have infinite solutions)  

-3x+y=6  --> y=3x+6

ax+2y=4 --> y=-ax/2 +2

3= -a/2

a=-6