9xy(x-y)(x+1)-3y(x-y)(3x+2y)+6y2(x-y)(x+1),其中x=-13,y=2.-数学

题目简介

9xy(x-y)(x+1)-3y(x-y)(3x+2y)+6y2(x-y)(x+1),其中x=-13,y=2.-数学

题目详情

9xy(x-y)(x+1)-3y(x-y)(3x+2y)+6y2(x-y)(x+1),其中x=-
1
3
,y=2.
题型:解答题难度:中档来源:不详

答案

9xy(x-y)(x+1)-3y(x-y)(3x+2y)+6y2(x-y)(x+1)
=9xy(x2+x-xy-y)-3y(3x2+2xy-3xy-2y2)+6y2(x2+x-xy-y)
=9x3y+9x2y-9x2y2-9xy2-9x2y+3xy2+6y3+6x2y2+6xy2-6xy3-6y3
=9x3y-3x2y2-6xy3,
x=-class="stub"1
3
,y=2时,原式=9×(-class="stub"1
3
)3×2-3×(-class="stub"1
3
)2×22-6×(-class="stub"1
3
)×23
=-class="stub"2
3
-class="stub"4
3
+16
=14.

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