x(x-2)分之x+2减去(x-2)方分之x-1
=[(X+2)(X-2)]/[X(X-2)²] - [X(X-1)]/[X(X-2)²]
=(X²-4-X²+X)/[X(X-2)²]
=(X-4)/[X(X-2)²]
=(X-4)/(X³-4X²+4X)