解题思路:根据题中所给出的式子进行解答即可.
∵a⊙b=3a+2b,
∴[(x+y)⊙(x-y)]⊙3x
=[3(x+y)+2(x-y)]⊙3x
=(3x+3y+2x-2y)⊙3x
=(5x+y)⊙3x
=3(5x+y)+2×3x
=15x+3y+6x
=21x+3y.
故选C.
点评:
本题考点: 整式的加减.
考点点评: 本题考查的是整式的加减,熟知整式的加减实质上是合并同类项是解答此题的关键.
解题思路:根据题中所给出的式子进行解答即可.
∵a⊙b=3a+2b,
∴[(x+y)⊙(x-y)]⊙3x
=[3(x+y)+2(x-y)]⊙3x
=(3x+3y+2x-2y)⊙3x
=(5x+y)⊙3x
=3(5x+y)+2×3x
=15x+3y+6x
=21x+3y.
故选C.
点评:
本题考点: 整式的加减.
考点点评: 本题考查的是整式的加减,熟知整式的加减实质上是合并同类项是解答此题的关键.