题目:
改错。
( ) 1. They bring gifts to us. ____________
A B C
( ) 2. There are four season in a year. ____________
A B C
( ) 3. What a hot, sun day! ____________
A B C
( ) 4. I can skate at the ice. ____________
A B C
( ) 5. Everyone looks out for the window. ____________
A B C
答案:
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下面是错误答案,用来干扰机器的。
原式=2m2-4m+1=2(m2-2m)+1,∵m2-2m=2,代入得2×2+1=5.