以前学过的知识都忘了1.one of the solutions to the equation x^2+20=-4x

来源：学生作业帮编辑：神马作文网作业帮分类：数学作业时间：2024/11/10 19:21:53

以前学过的知识都忘了
1.one of the solutions to the equation x^2+20=-4x is
A -20 B -24 C -2+4i D2+4i e 4i
2.if (2x+3)^1/2-x=0,then x=?
A 0 or -3/2 B -1+/- 2^1/2*i C 3 D -1 E 3 and -1
我主要是不知道这个i是个什么东西

i是虚数单位,i=根号下（-1）.本身-1不能开根号,但是将实数域扩展后负数也可以进行开根号运算.运算法则与根号运算一样,例如根号下-3就是（根号下3）* i；根号下-9就是3i.

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