(x,y)稱為數(shù)對,其中x,y都是任意實數(shù),定義數(shù)對的加法、乘法運算如下:
(x1,y1)+(x2,y2)=(x1+x2,y1+y2)
(x1,y1)•(x2,y2)=(x1x2-y1y2,x1y2+y1x2),則( )不成立.
A.乘法交換律:(x1,y1)•(x2,y2)=(x2,y2)•(x1,y1)
B.乘法結合律:(x1,y1)•(x2,y2)•(x3,y3)=(x1,y1)•[(x2,y2),(x3,y3)]
C.乘法對加法的分配律:(x,y)•[(x1,y1)+(x2,y2)]=[(x,y)•(x1,y1))+((x,y)•(x2,y2)]
D.加法對乘法的分配律:(x,y)+[(x1,y1)•(x2,y2)]=[(x,y)+(x1,y1)]•[(x,y)+(x2,y2)]
【答案】分析:根據定義數(shù)對的加法、乘法運算,逐一檢驗.
解答:解:A、由(x2,y2)•(x1,y1)
=(x1x2-y1y2,x1y2+y1x2)
=(x1,y1)•(x2,y2)可知,乘法交換律成立,A正確;
B、由[(x1,y1)•(x2,y2)]•(x3,y3)
=(x1x2-y1y2,x1y2+y1x2)•(x3,y3)
=(x1x2x3-y1y2x3-x1y2y3-y1x2y3,x1x2y3-y1y2x3+x1y2x3+y1x2x3)
=(x1,y1)•(x2x3-y2y3,x2y3+y2x3)=(x1,y1)•[(x2,y2)•(x3y3)]可知,乘法結合律成立,B正確;
C、由(x,y)•[(x1,y1)+(x2,y2)]
=(x,y)•(x1+x2,y1+y2)
=[x(x1+x2)-y(y1+y2),x(y1+y2)+y(x1+x2)]
=(xx1-yy1,xy1+yx1)+(xx2-yy2,xy2+yx2)
=[(x,y)•(x1,y1)]+[(x,y)•(x2,y2)]可知,乘法對加法的分配律成立,C正確;
D、由(1,0)+[(1,0)•(1,0)]
=(1,0)+(1,0)
=(2,0)≠(2,0)•(2,0)
=[(1,0)+(1,0)•((1,0)+(1,0))]可知,加法對乘法的分配律不成立,D錯誤.
不成立的是D.
故選D.
點評:本題考查了整式的混合運算,運用了新定義對幾種運算律進行檢驗,還運用到了特殊值法解題.