对于有理数a、b,定义a⊙b=3a+2b,则[(x+y)⊙(x-y)]⊙3x化简后得( )
A. 0
B. 5x
C. 21x+3y
D. 9x+6y
人气:110 ℃ 时间:2019-10-11 17:36:47
解答
∵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.
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