若a,b都是質數,如果a square+b=2005,a+b=?
回答 (2)
2006-10-22 7:33 am
✔ 最佳答案
應該計唔倒的...除左2之外. 質數都係 "單數"...
而"單數"嘅square, 亦係"單數"...
將 2005 - "單數" = 雙數...
但雙數唔會係質數...
所以. 我地用唯一係雙數嘅質數黎prove...
2^2 + b = 2005
b = 2001
however, 2001係三嘅倍數...
所以... 應該係冇答案的吧...
2006-10-21 5:53 am
No answer!!!
Because a odd number square must be a odd number and an even number square must be an even number.So a and b must be a odd number and an even number.We know,just 2 is the even number and a prime number.Therefore,a or b is 2.
If a is 2 ,then 2 times 2 is 4:
4+b=2005
b=2001
Not the answer (Because 2001can divided by 3)
If b is 2,then
a+2=2005
a=2003
Not the answer (Because 2003 is not a square number)
Because a odd number square must be a odd number and an even number square must be an even number.So a and b must be a odd number and an even number.We know,just 2 is the even number and a prime number.Therefore,a or b is 2.
If a is 2 ,then 2 times 2 is 4:
4+b=2005
b=2001
Not the answer (Because 2001can divided by 3)
If b is 2,then
a+2=2005
a=2003
Not the answer (Because 2003 is not a square number)
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