分数加减(用方程).doc

文档介绍：+X= - X = X-=2
+X = X-= +X= X + –=
-X= -x= +x= X-+=
-x = X -= X-= ++X=3
X + = +X= X-=3 + + x =
X+= -X= X + = x - =
x += x - = +x =
X+= X-= X-= X+=
+X= + x = + x = X+=
x - = X + = - x= x +( + )=2
X-= X- = X- =
x + = χ- = +
- x= χ+= + x = x - =
x-=
1-χ= x--=