先化简再求值:4xy²-[6xy-3(4xy-2)-x²y]+1,其中x=2,y=-1/2
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/05 11:21:52
![先化简再求值:4xy²-[6xy-3(4xy-2)-x²y]+1,其中x=2,y=-1/2](/uploads/image/z/8733532-4-2.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A4xy%26%23178%3B-%5B6xy-3%284xy-2%29-x%26%23178%3By%5D%2B1%2C%E5%85%B6%E4%B8%ADx%3D2%2Cy%3D-1%2F2)
先化简再求值:4xy²-[6xy-3(4xy-2)-x²y]+1,其中x=2,y=-1/2
先化简再求值:4xy²-[6xy-3(4xy-2)-x²y]+1,其中x=2,y=-1/2
先化简再求值:4xy²-[6xy-3(4xy-2)-x²y]+1,其中x=2,y=-1/2
原式等于
4xy²-[6xy-12xy+6-x²y]+1
=4xy²+6xy-6+x²y+1
=4xy²+x²y+6xy-5然后把
x=2,y=-1/2
带入得4-2-6+1=-3
4x²y-[6xy-3(4xy-2)-x²y]+1
=4x²y-[6xy-12xy+6-x²y]+1
=4x²y-6xy+12xy-6+x²y+1
=(4x²y+x²y)-(6xy-12xy)+1
=5x²y+6xy+1
把x=2,y=-1/2.代入
5x...
全部展开
4x²y-[6xy-3(4xy-2)-x²y]+1
=4x²y-[6xy-12xy+6-x²y]+1
=4x²y-6xy+12xy-6+x²y+1
=(4x²y+x²y)-(6xy-12xy)+1
=5x²y+6xy+1
把x=2,y=-1/2.代入
5x²y+6xy+1
=5*(2^2)*(-1/2)+6*2*(-1/2)+1
=-10-6+1
=-15
收起
带入计算就行了,过程为:
4xy²-[6xy-3(4xy-2)-x²y]+1
=4*2*1/4-[6*2*(-1/2)+3*6+2]+1
=2-14+1
=-11
直接从左到右化难道不行吗?
4xy²-[6xy-3(4xy-2)-x²y]+1
=4xy²-[6xy-12xy+6-x²y]+1
=5xy²-6xy+1
带入XY得
5*2*(-1)*(-1)-6*2*(-1)+1=23或
5*2*(2)*(2)-6*2*(2)+1=15
原式=4xy2-[6xy-12xy+6-x2y]+l
=4xy2-[-6xy+6-x2y]+1
=4xy2十6xy-6+x2y+1
=4xy2十6xy十x2y一5
当x=2,y=-1/2时
原式=2一6一2-5
=-11
你把计算查一下,可能有错