明天考试，紧急求助！！！

xingzhihua

1）  一个序列，从第三位数起，每个数都与它前面连续的两个数的和有关，the number is the sum of the 2 numbers in the sum is odd or ½ if the sum of the 2 numbers are even, the forth number is 7 and the fifth number is 5, what is the first number?

LittleLilyLiAng

the number is the sum of the 2 numbers in the sum is odd or ½ if the sum of the 2 numbers are even这句话是什么意思?

sharleane

1st, 2nd, 3rd, 7, 5
3rd+7=5*2, so 3rd=3

1st, 2nd, 3, 7, 5
2nd+3=7, so 2nd=4

1st, 4, 3, 7, 5
1st+4=3*2, so 1st=2

I believe the answer 2 is right, how do you think?

LittleLilyLiAng

sorry,这题说的不太清楚，我不知道是什么意思.