Question

一道初一数学题，在线等，急急急，谢谢了

已知xy^2=-6
求-xy(x^3y^7-3x^2y^5-y)的值

Answer 1

因为xy^2=-6
所以(xy^2)^2=(-6)^2,x^2y^4=36
即(xy^2)^3=(-6)^3,x^3y^6=-216

-xy(x^3y^7-3x^2y^5-y)
=-xy[(x^3y^6)*y-3(x^2y^4)*y-y]
=-xy[(xy^2)^3*y-3(xy^2)^2*y-y]
=-xy(-216*y-3*36*y-y)
=-xy*(-325y)
=325xy^2
=325*(-6)
=-1950
初一啊,挺难的了

Answer 2

xy^2=-6
所以(xy^2)^2=(-6)^2,x^2y^4=36
(xy^2)^3=(-6)^3,x^3y^6=-216

-xy(x^3y^7-3x^2y^5-y)
=-xy[(x^3y^6)*y-3(x^2y^4)*y-y]
=-xy[(xy^2)^3*y-3(xy^2)^2*y-y]
=-xy(-216*y-3*36*y-y)
=-xy*(-325y)
=325xy^2
=325*(-6)
=-1950

Answer 3

原式
=-x^4y^8+3x^3y^6+xy^2
=-(xy^2)^4+3(xy^2)^3+xy^2

将xy^2=-6代入
原式
=-(-6)^4+3(-6)^3+(-6)
=-1296-648-6
=-1950

Answer 4

因为xy^2=-6
所以(xy^2)^2=(-6)^2,x^2y^4=36
所以(xy^2)^3=(-6)^3,x^3y^6=-216

-xy(x^3y^7-3x^2y^5-y)
=-xy[(x^3y^6)*y-3(x^2y^4)*y-y]
=-xy[(xy^2)^3*y-3(xy^2)^2*y-y]
=-xy(-216*y-3*36*y-y)
=-xy*(-325y)
=325xy^2
=325*(-6)
=-1950
一定给偶分