先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/30 20:30:32
![先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2](/uploads/image/z/3010195-19-5.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC%3A%283x%26%23178%3B%2By%26%23178%3B%29-%5B-3x-2%28x%26%23178%3B-xy%29%2By%26%23178%3B%5D%2C%E5%85%B6%E4%B8%ADx%3D-1%2Cy%3D-2)
先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
(3x²+y²)-[-3x-2(x²-xy)+y²]
=3x²+y²+3x+2(x²-xy)-y²
=3x²+y²+3x+2x²-2xy-y²
=5x²+3x-2xy
把x=-1,y=-2代入得:
5-3-4=-2