徐永強數學- p-set2-20

[邁向高等學府]

Is x odd?
1. a-b=x and b-c=x, where a, b, & c are distinct prime numbers
2. x is the product of 2 consecutive prime numbers

為何答案為A...?

我認為是D耶…
條件2，2*3=6不就是偶數嗎?

[汪汪北鼻]

Is x odd?
1. a-b=x and b-c=x, where a, b, & c are distinct prime numbers
2. x is the product of 2 consecutive prime numbers

1)sufficient, if a,b,c are prime numbers, their difference must be even. Therefore X must not be odd

2)insufficient, 2*3=6(even), 3*7=21(odd) we are not sure whether x is odd or even.

hence, the anwer is A