20 Caot Sation: y yo e △x c-ox a △X AX M c+///-△x MM 1-4x) shr aw allalin cann lr t aAX→ (1-∞x co comi linP stanly co coEn lo &tale y。//-c4x //-△x d x fov 3/&s d cy //-a△x/≤1 //-a4x/> /-k×//aha的~y