Hello Zoom!! Let me try to explain why it is E. =)

In 1, the equation will be even if X is even, if y+5 is even, or if both are even. The general rule is even x even = even and odd x even = even. Since y can equal any number, 1 alone is not sufficient.

In 2, you know nothing about x so it alone is not sufficient.

When we add the two equations together, you can try to plug in numbers for y in (2). You'll notice that only when y=an odd number will equation (2) equate to an even result. If we plug in an odd number for y into (1), y=5 will always be even. Going back to our general rules, x can be both even or odd to make (1) true.

I hope that helps!!

zoom wrote:

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

1 - x(y+5) is even

2 - 6y^2 + 41y + 25 is even

I answered C but apparently it's wrong

My logic :

1 alone is not sufficent

2 alone is not sufficent

now if we take take them together, from 2 we know that 41y is odd thus y is odd. Since y is odd, x must be even.

The right answer is E but don't understand why !! help