gwd 18 36

rosemarys

Q36:

If x and y are integers, is y an even integer?

(1) 2y – x = x² – y²

(2) x is an odd integer.

jojof5460

选C, 由2个条件可以推出Y 是 偶数

lemonees

y^2+2y=x+x^2

(y+1)^2=x^2+x+1

x odd,----> x^2+x+1 odd,----> y+1 odd--->y even

x even----->x^2+x+1 odd,---------->y even

answer:A