Question

若m是一個數，且||m|+2m|=3，則m等于______．

Answer 1

當m＞0時，|m|=m，∴||m|+2m|=|m+2m|=3m=3
∴m=1
當m＜0時，|m|=-m，∴||m|+2m|=|-m+2m|=|m|=3
∴m=-3
所以m等于1或-3．