设原正方形边长为x
(x-1)*(x-2)=12
x1=5 x2=-2(不合题意舍去)
答：原正方形空地的边长为5米设原正方形边长为x剩余空地的长为 x-1宽为 x-2面积为(x-1)*(x-2)=12 x^2-3x-10 = 0(x-5)(x+2) = 0x1=5x2=-2