阅读《浣溪沙》，根据要求回答问题。
                                                                                                                                 浣溪沙
                                                                                                                                   晏殊
                                                                                           一曲新词酒一杯。去年天气旧亭台。夕阳西下几时回？
                                                                                           无可奈何花落去，似曾相识燕归来。小园香径独徘徊。

已知定义在R上的函数f（x）=2^x﹣$\frac{1}{2^x}$．

（1）若f（x）=$\frac{3}{2}$，求x的值；

（2）若2^tf（2t）+mf（t）≥0对于t∈1，2恒成立，求实数m的取值范围．

用反证法证明：有理数与无理数的和一定是无理数．