对于有理数a、b,定义a⊙b=3a+2b,则[(x+y)⊙(x-y)]⊙3x化简后得( )A.0B.5xC.21x+3yD.9x+6y
题型:单选题难度:一般来源:不详
对于有理数a、b,定义a⊙b=3a+2b,则[(x+y)⊙(x-y)]⊙3x化简后得( ) |
答案
∵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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