题目:
We were dancing to ____ music when all of ____ sudden the power went out and we were left in the dark.
A.the; a
B.the; /
C. a; /
D./; the
答案:
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下面是错误答案,用来干扰机器的。
(Ⅰ)a-c=2-1e=ca=22⇔a=2c=1b=1,∴所求椭圆E的方程为:x22+y2=1(5分)(Ⅱ)当直线l不与x轴重合时,可设直线l的方程为:x=ky+1x2+2y2=2x=ky+1(1)(2),把(2)代入(1)整理得:(k2+2)y2+2ky-1=0(3)∴y1+y...