1, x and y are integers, and "xy+x 2 is odd" means that x*(x+y) is odd.

I think this question asks which combination is correct. Because looking at it alone, ① ② ③ cannot be deduced, which means that A and B are wrong. If x is odd and y is odd, then x+y is even and x*(x+y) is even, so c is wrong. If y and x+y are odd numbers, then x is even, and x*(x+y) is even, then e is wrong and there is only X.

2. How many possibilities does n have to make the value of (2n+ 1) (3n- 1) negative?

This problem is to solve inequalities. According to the meaning of the question,

Either 2n+1; 0

Either: 2n+1>; 0 and 3n- 1

The conclusion of the first set of inequalities is that there is no N < (n; 1/3)

The conclusion of the second set of inequalities is-1/2.