If x = -|w|, which of the following must be true?
x =-w
x =w
x2= w
x2= w2
x3= w3
题目分析:
x =−|w|,, 两边同时平方得~$x^2 $~= ~$(−|w|)^2$~,~$x^2=w^2$~;
x=−|w|,得出x-w或者-w. A, B 肯定不对,x=±w, 则~$x^2=w^2$~,~$x^3=± w^3$~;
综上:答案就是D.
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