作业帮若丨x丨=2,求式子3x²-[7x²-2(x²-3x²）-2x]的值；
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/05 11:35:49
![若丨x丨=2,求式子3x²-[7x²-2(x²-3x²）-2x]的值；](/uploads/image/z/4325697-9-7.jpg?t=%E8%8B%A5%E4%B8%A8x%E4%B8%A8%3D2%2C%E6%B1%82%E5%BC%8F%E5%AD%903x%26%23178%3B-%5B7x%26%23178%3B-2%28x%26%23178%3B-3x%26%23178%3B%EF%BC%89-2x%5D%E7%9A%84%E5%80%BC%EF%BC%9B)
若丨x丨=2,求式子3x²-[7x²-2(x²-3x²）-2x]的值；
若丨x丨=2,求式子3x²-[7x²-2(x²-3x²）-2x]的值；
若丨x丨=2,求式子3x²-[7x²-2(x²-3x²）-2x]的值；
∵|x|=2
∴x=2或x=-2
3x²-[7x²-2(x²-3x²）-2x]
=3x²-(7x²-2x²+6x²-2x)
=3x²-7x²+2x²-6x²+2x
=-8x²+2x
当x=2时,原式=-8×2²+2×2=-28
当x=-2时,原式=-8×(-2)²+2×(-2)=-36
3x²-[7x²-2(x²-3x²）-2x]
=3x²-7x²+2x²-6x²+2x
=-8x²+2x
丨x丨=2
原式=-8x4±4
=-36或-28