pp2-ps-162 (求思路 )

Kath1985

162.17416-!-item-!-187;#058&011441

If x is an odd integer, which of the following is also an odd integer?



(A) 2x

(B) 4x + 2        
(C) x2 + 3        => 1*2+3   奇數
(D) x2 + x + 3 => 1*2+1+3 偶數
(E) x2 + 2x + 1 => 1*2+2*1+1 奇數

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【答案】D
黃色部分是我舉的例子 既然如此 答案應該是C、E呀 想不通.......

草稿纸

x2是x平方