Answer:
A = 0
Explanation:
System of equations
We have a general equation
Ax + By = 0
We are required to find the value of A, knowing that the ordered pairs (x,y)=(-7,-4) and (14,2) meet the condition.
Use (-7,-4):
A(-7)+B(-4)=0
Or, equivalently:
-7A-4B=0
Use (14,2):
A(14)+B(2)=0
Dividing by 2:
7A+B=0
Adding both equations:
-7A - 4B + 7A + B =0
Simplifying:
-3B = 0
B = 0
If follows that, also
A = 0