To solve this problem you must apply the proccedure shown below:
Points: A(0, 1), B(3, 7), C(4, 4), D(x,y)
1. You must make a system of equations by applying the slope formula:
The slope AB=CD:
(y-4)/(x-4)=(7-1)/(3-0)
3y=6x-12 (First equation)
The slope of AD=BC:
(y-1)/(x-0)=(4-7)/(4-3)
y=-2 (Second equation)
2. When you solve it, you obtain:
x=1
y=-2
The answer is: (1,-2)