已知(x-2)2+|xy-4|=0,求3x2y+{-2x2y-[-2xy+(x2y-4x2)-xy]+xy2}.

问题描述:

已知(x-2)2+|xy-4|=0,求3x2y+{-2x2y-[-2xy+(x2y-4x2)-xy]+xy2}.

3x2y+{-2x2y-[-2xy+(x2y-4x2)-xy]+xy2}
=3x2y+{-2x2y-[-2xy+x2y-4x2-xy]+xy2}
=3x2y+{-2x2y+2xy-x2y+4x2+xy+xy2}
=3x2y-2x2y+2xy-x2y+4x2+xy+xy2
=3xy+xy2+4x2
∵(x-2)2+|xy-4|=0,
∴x-2=0,xy-4=0,
∴x=2,y=2,
把x=2,y=2代入原式得:
=3×2×2+2×22+4×22
=36.
答案解析:根据整式加减运算的顺序,先去括号,再合并同类项,然后根据(x-2)2+|xy-4|=0,求出x,y的值,再代入即可.
考试点:整式的加减—化简求值;非负数的性质:绝对值;非负数的性质:偶次方.


知识点:此题考查了整式的化简,用到的知识点是去括号、合并同类项、绝对值和偶次方的性质,关键是求出x,y的值.