为了增强同学们的意志品质，某校八年级六班在学习了思想品德第三课《优良的意志品质》后，召开了一次以“磨砺意志，学会坚强”为主题的主题班会。假如你是该班的一名学生，请你参加以下活动： 

Mrs. Black lives in a small village. Her husband is dead. Her son, Jack, lived with her. He worked in a shop in the village, but then he found a job in town named Green Sea. He went to live there. Mrs. Black was very angry. She got on a train and went to see her son. Then she said to him, "Jack, why do you never telephone me?"
Jack laughed, "But, mother, you haven’t got a telephone. "No." She answered, "I haven’t, but you have got one. "

如果函数f（x）=x²+2（a﹣1）x+2在区间4，+∞）上是递增的，那么实数a的取值范围是（　　）

汉译英