[問題]GWD23-19

[gozui[origen]]

For each positive integer n, the integer n* is defined by n* = n^2+ 1. What is the value of the positive integer k ?
(1) When k is divided by 4, the remainder is 1.
(2) 18 ≤ k* ≤ 36

尋求高人指點, 感激不盡

[Frankts]

答案是B嗎

[gozui[origen]]

是的, 答案是B

請問是如何確定的?

[FIG]

For each positive integer n, the integer n* is defined by n* = n^2+ 1. What is the value of the positive integer k ?
(1) When k is divided by 4, the remainder is 1.
(2) 18 ≤ k* ≤ 36

1.只說明k是4的倍數加1
2. k* = k^2+ 1 & 18 ≤ k* ≤ 36 得知 k為5

Ans:b

[Frankts]

1選項 K被4除於1 所以得K等於4X+1 不能確定
2選項 18 ≤ k* ≤ 36 又k*=k^2+ 1
所以當K=4 k*=17 不合條件
K=5 k*=26 合條件
K=6 k*=37 不合條件
所以得知K=5
希望沒有遺漏什麼 也希望有所幫助

[gozui[origen]]

感謝Frankts 及 FIG的熱心協助, 我終於明白了
你們會得萬福的! ^.^