分式加减法

注意，分子在上，分母在下

ab/c-bc/a
通分
=a^2b/ac-bc^2/ac
=(a^2b-bc^2)/ac

c/ab-a/bc
=C^-a^/abc
=[c+a]*[c-a]/[abc]

ab/c-bc/a
=a^b-bc^/ac
=b[a+c][a-c]/ac

ab/c-bc/a
=(a^2b-bc^2)/ac
=b*(a+c)*(a-c)/ac

ab/c-bc/a
=(a^2b-b^2c)/ac
=b(a^2-bc)/ac

ab/c+bc/a=(a ab + bc c)/(a c)

没看懂