Answer:
0
Explanation:
Multiplying out the given expression, we get acx^2 - adxy + bcxy - bdy^2.
Since ac = 18 and bd = 50, this expression becomes 18x^2 - (ad - bc)xy -50y^2. But ad=bc, so this reduces to 18x^2 - 0 - 50y^2, or 18x^2 - 50y^2. In other words, the coefficient of the xy term is 0.