作业帮先化简,再求值：3x²—[2x²y—（xy—x²）]+4x²y,其中x=—1,y=2.
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/06 01:27:06
![先化简,再求值：3x²—[2x²y—（xy—x²）]+4x²y,其中x=—1,y=2.](/uploads/image/z/2518189-61-9.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A3x%26%23178%3B%E2%80%94%5B2x%26%23178%3By%E2%80%94%EF%BC%88xy%E2%80%94x%26%23178%3B%EF%BC%89%5D%2B4x%26%23178%3By%2C%E5%85%B6%E4%B8%ADx%3D%E2%80%941%2Cy%3D2.)
先化简,再求值：3x²—[2x²y—（xy—x²）]+4x²y,其中x=—1,y=2.
先化简,再求值：3x²—[2x²y—（xy—x²）]+4x²y,其中x=—1,y=2.
先化简,再求值：3x²—[2x²y—（xy—x²）]+4x²y,其中x=—1,y=2.
化简：3x²—[2x²y—（xy—x²）]+4x²y
=3x²-（2x²y-xy+x²）+4x²y
=3x²-2x²y+xy-x²+4x²y
=2x²+2x²y+xy
将x=-1,y=2 代入代数式中,得：2x²+2x²y+xy=4