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                                                                                                                                 读(节选)  
                                                                                               人之一生．读之一生    读海，胸怀将变得辽阔
                                                                                               从春读到夏，从小读到大  读月，方知阴晴圆缺
                                                                                               读雨，方知万物可以滋润，心灵能够洗涤    

                                                                                               读日，便不再惋惜日近黄昏
                                                                                               读雪，能领悟到嚣的纯洁，感受到冬的春意             用心品读，细细感悟
                                                                                                读风，就能触摸d4)11的脉搏，聆听天地的呼吸      阴雨中能读出晴空
                                                                                               读霞，才能于苍茫中发现辉煌，展示自己韵不屈     枯黄中能读出翠绿
                                                                                               读花，你学会倾听     沙漠中能读出清泉
                                                                                               读树，你学套成长       黑暗中能读出晨曦
                                                                                               读山，你学会攀登                                     

                                                                                                                                                                                                                                          (诗歌有删改)

现定义运算“★”，对于任意实数a、b，都有a★b=a²-3a+b，如：3★5=3²-3×3+5，若x★2=6，则实数x的值是（）