经过圆C:(x+1)2+(y-2)2=4的圆心且斜率为1的直线方程为[ ]
A.x-y+3=0
B.x-y-3=0
C.x+y-1=0
D.x+y+3=0
答案:A
方程(1+a)x2-4ax+2a+3=0
(1)若方程存在不相等的两实数根,求a的范围.
(2)若方程的根均小于0,求a的范围.
苯乙酸盐