factors out to . This isn't the difference between two squares. Remember that , but this isn't the same as

There is no reason to factor it anyway, it's factored enough for you already. The only zeros of this function are and .

So now set up your test intervals to find were the function is greater than or EQUAL to zero. So you know your intervals should be closed at and . Let me know if you need more help. Lucky for you, I'll be here for a few mins.

Test intervals: