00:02
In this problem, we're asked to figure out which of the following conjectures is false.
00:08
Okay? so we're going to look at each conjecture, try out a few examples, and see if we can determine whether or not the statement is true or false.
00:16
So the first one, if x is odd, then x plus one is even.
00:21
So let's just try out a few of them.
00:24
So let's pick an odd number.
00:25
So we can start with three for an odd number.
00:29
We'll let x equal three so then three plus one is four okay so far so good uh let's try another odd number let's try x equals five well then five plus one is six all right this is looking promising what if i did a negative number like x equals negative seven well then negative seven plus 1 is negative 6.
01:08
That's still an even number.
01:10
I just noticed a typo here.
01:12
This should be 5 plus 1.
01:16
So it looks like when you have an odd number and you add one to it, it just takes you to whatever the next number is, which we know that odd and even numbers go back and forth between each other.
01:28
So if we start with an odd and add one to it, the next one's going to be even.
01:32
So this guy looks like it's true.
01:35
Let's go to the next one.
01:36
The sum of two odd numbers is even.
01:39
Okay, so once again, let's start with some odd numbers, add them together, and see what we get.
01:44
So let's start with two odd numbers, but have them both be positive.
01:49
So one plus three are both odd.
01:53
Okay? so one plus three gives us four.
01:56
That's even.
01:58
Let's try two negative.
02:00
So let's go negative five plus...