若三条直线2x+3y+8=0,x-y-1=0和x+ky=0相交于一点,求k的值。
解:其交点坐标为:,解得(-1,-2),
直线x+ky=0也经过交点,
所以有,-1-2k=0,即。
I'd like to buy a new computer, but I don't know _______. [ ]
A. where could they buy it
B. where can I get it
C. I should choose which
D. which I should choose
慢性盘状红斑狼疮在口腔黏膜的好发部位是()。
A.颊部黏膜
B.舌背黏膜
C.下唇唇红
D.上唇唇红
E.上腭黏膜