12. ( ) 已知多項式f (x)除以x -1的餘式為 9,且f (x)除以x + 4的餘式為-3。若f (x)除以(x -1)(x + 4)的餘式為ax+b ,下列敘述何者錯誤?(A)f (1) 9 =(B)f(x)的各項係數和為 9 (C) a=