[問題] GWD 7- Q36

[kwtluck]

Q36:
If a and b are positive integers such that a - b and a/b are both even integers, which of the following must be an odd integer?

A.a/2
B.b/2
C.(a+b)/2
D.(a+2)/2
E.(b+2)/2

Answer: D

請教各位大大,為什麼答案是D Thanks!!~~

[kwtluck]

自己頂一下

[lance921]

a/b is even integer -> a = 2*b*n 所以a是 even integer
a-bis even integer & a是 even integer -> b是 even integer
a/b is even integer & b是 even integer -> a 為4的倍數
(4n+2)/2 一定是odd integer

[kwtluck]

**感謝lance921大大熱情解題**
Thanks!!~~