∵a=7/3,b=-2/3∴[(a-b)^2-(a+2b)(a-2b)]/(-4b)=[a²-2ab+b²-(a²-4b²)]/(-4b)=[5b²-2ab]/(-4b)=[5b-2a]/(-4)=[5(-2/3)-2*7/3]/(-4)=(-24/3)/(-4)=2