Question

If n is even, which of the following cannot be odd?

I n + 3
II 3n
III n² - 1

Answer 1

let n = 2
2+3 = 5
3*2 = 6
2^2-1 = 3

Answer 2

can you answer now?

Answer 3

if n is even 3 is always odd

Answer 4

you can do this in a more general way
if n is even the n = 2k for some integer k
n+3 = 2k+3 is always odd
3n = 3*2k = 6k is always even
n^2-1=(2n)^2-1 = 4n^2-1 is always odd