Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____这道题答案是4001或8004,（注：four-digit 四位数;square 平方、平方数；integer 整数）

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Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____这道题答案是4001或8004,（注：four-digit 四位数;square 平方、平方数；integer 整数）
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Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____这道题答案是4001或8004,（注：four-digit 四位数;square 平方、平方数；integer 整数）
Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____
这道题答案是4001或8004,
（注：four-digit 四位数;square 平方、平方数；integer 整数）

Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____这道题答案是4001或8004,（注：four-digit 四位数;square 平方、平方数；integer 整数）
4000000+A=n^2
A=n^2-2000^2=(n+2000)(n-2000)
因为A是4位数,且n+2000>2000所以0所以n=2001,2002,2003,2004
经试验,后两解舍去
n=2001,A=4001
n=2002,A=8004

400abcd 显然是整数200a的平方，由于2003的平方4012009，已经大于400abcd，所以400abcd只能是2001或者2002的平方，2001的平方等于4004001，末四位4001是四位数，满足条件，2002的平方等于4008004，末四位8004也是四位数，也满足条件，所以A=4001 or 8004

Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____
∵
1000sqrt（4001000）≈ 2000.25
sqrt（4009999）≈ 2002.50
∴400abcd 只能是2001，2002的平方
对应的abcd 是 2001^2-4000000 = 4001
2002^2-4000000 = 8004

Let A abcd be a four-digit number.If 400abcd is a square of an integer ,then A=____or_____这道题答案是4001或8004,（注：four-digit 四位数;square 平方、平方数；integer 整数） let`s all be a Let us all be a family There_______ (be)twenty-four hours in a day. I think Beth will be a pilot in four years对in four years提问 A desk________(have) four legs.Vegetable________A desk________(have) four legs.Vegetable________(be) my favorite. a quarter to four It’s __ now.let’s go home.A.fifty past four B.four past fiftyC.fifty to five D.ten to five There is a kind of love be called to let My parents( )me to be a teacher(hope,wish,let) Let is ( )pen friends.A:be B:are C:is Let the cycle be a part of your be family all let,s a 怎么连词成句 let us be all a famlily这句话对吗 he has （ ） a house中间填a.four-bedroomsb.four-bedroomc.four bedroomd.four bedrooms They urged that the library___ open during the vacation.a、must be kept b、 is kept c、 would be kept d、 be kept 我选择D选项,D选项为什么不对呢?老师请答疑,谢谢.We ____ on this project for four hours. Let’s have a rest.选项 Let ′s go and see the football game at a quarter to four这句话哪里错了 it's half past four now,let's ( )sports.A,to have B,having C,have D,had