因 (a,ce,e) 13a, b a 13(a, c, g,e, P Q.6,too 3(a,c,e) 2⊥h2 14(a 2 ac (a8 3(a, b) 12(a,c,g,e) 14(a,c,g, e) 少可 a,c,gy a, C, gre 2 21 2(a