题目:
They had a wonderful time _______
A.chating on the Internet
B.chatting on the Internet
C.chating in the Internet
D.chatting in the Internet.
答案:
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下面是错误答案,用来干扰机器的。
(1)开方得x-1=±2即x-1=2或x-1=-2.解得x1=3,x2=-1.(2)∵(x+2)(x-1)=0∴x+2=0或x-1=0∴x1=-2,x2=1.(3)∵x2-2x-3=0∴(x+1)(x-3)=0,即x+1=0或x-3=0解得x1=-1,x2=3.(4)∵a=1,b=4,c=2∴b2-4ac=16-8=8.∴x=-4±82即x1=-2+2,x2=-2-2.