4x^2y-[6xy-2(4xy-2)-x^2y]+1,其中x=-1/2,y=4

题目

4x^2y-[6xy-2(4xy-2)-x^2y]+1,其中x=-1/2,y=4
五分钟之内~

答案

4x^2y-[6xy-2(4xy-2)-x^2y]+1
=4x^2y-6xy+8xy-4+x^2y+1
=5x^2y+2xy-3 把x=-1/2,y=4带入
=5（-1/2）²×4+2（-1/2）×4-3
=5-4-3
=-2