已知某一次函数的图象经过点A(0,2),B(1,3),c(a,1)三点;求这个一次函数的解析式及a的值。
解:设一次函数的解析式为
则由条件得
解之得:
即一次函数的解析式为:
I didn 't see her in the meeting-room this morning. She ______ at the meeting. [ ]
A. mustn’t have spoken
B. shouldn’t have spoken
C. needn’t have spoken
D. couldn’t have spoken
试述动脉导管未闭的临床症状、心脏体征及X线检查、心电图特点。