题目

When was the last time you thought about breathing? Most people usually do not. When we are healthy, breathing happens· naturally and easily. Without much effort on our part, the human respiratory（呼吸的）system works hard. Experts say we take about 20,000 breaths every day.One such expert James Hoyt with the University of Colorado's Health Pulmonology（肺科）Clinic notes that our respiratory muscles are working every minute of the day. A muscle called the diaphragm separates the chest and abdominal cavities（腹腔）. As we breathe in, the diaphragm（横膈膜）tightens. The ch将直线y=2x+1向下平移3个单位长度后所得直线的解析式是 ．