1. $    .
2. =   #    
    (  ).
3. D#     # -2  20.
0,    
    
 ,     
 .
Y\
zt{T[WXXTy__UGGGY\zt{T[WXXTy__UGGGY\ YWW^TXXTY_GGG㝘䟸GYa\]aY[YWW^TXXTY_GGG㝘䟸GYa\]aY[