Hey asilvester635.
You did everything right as long as you evaluate the expression correctly as you have it.
Heres the equation to which where you'll need to plug in x and y
(-2y)(-2x) - [1 -2x -2y]
plug these in the equation given above... (x=1/3, y=1/3)
the answer is 1/3 but idk how the book got that answer...
here what I have so far after plugging in the x and y into the equation...
= (-2/3)(-2/3) - [1 - 2/3 - 2/3]
= 4/9 - [1 - 4/3]..... IM STUCK HERE..... did i do anything wrong??
Using R, (so there is no ambiguity) I plug that in and get:
> (-2/3)*(-2/3) - (1 - 2/3 - 2/3)
[1] 0.7777778
> 7/9
[1] 0.7777778
This matches youe answer of 7/9 and not an alternative.