When x=-1:

Ok that gives us a little more information.
If we implicitly differentiate with respect to t, from the very start, then we can apply our product rule, ya?

The right side is zero, derivative of a constant is zero.
Where x' is dx/dt and y' is dy/dt.
From here, plug in all the stuff you know:
y' = -3
x = -1
y = 4
and solve for x'.
Hope that helps!
Use the calculator to find:
169^2=169*169=28561
W^2+5w-66=0
Factor
(w+11)(w-6)=0
w+11=0
w=-11 (not possible - cant have negative length
w-6=0
w=6
L(6)=66
L=11
Width = 6
Length = 11
These two integers are -6 and -7