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Video transcript

so let's do a couple of examples of the number opposites exercise on Khan Academy just to make sure that we've really digested what it means to be the opposite of a number so they have a number line here and then they've marked some of the numbers with letters and this is ABCDE and then they say what can we say about point B and point B is one hash mark to the left of zero all right select all that apply so the first thing they say is B is equal to negative D so that means that B needs to be the opposite of D let's see if that's true D is here D is one hash mark to the right of 0 the opposite of D or negative D should be one hash mark to the left of 0 which is B B is the opposite of D B is negative D so this is true the next statement is B is the opposite of e what's the e is one two three hash marks to the right of 0 so the opposite of e should be one two three hash marks to the left of zero that is not B that is a B is not the opposite of e a is the opposite of e but that's just what they write here so we're not going to check that and then they say B is equal to negative B that's saying that B is the same thing as the opposite of B that is not true the opposite of B is going to go on the other side of the number line that's D which is not B so this is also not true this would have been true if they said C is equal to negative C because C is at 0 its 0 away from 0 C is 0 the opposite of 0 is going to be 0 away on the other side of the number line well that's still 0 away so 0 is negative 0 or we could have said C is equal to negative C that the only number for which that is true is 0 it's not going to be true for B because b is clearly not 0 so let's let's do let's do a couple of here what can we say about negative C all right so now C is 0 select all apply negative C is 0 yeah the negative of 0 is going to still be 0 the negative of 0 the opposite 0 is still going to be 0 the opposite of 0 well that's not going to be this number this is some nonzero number so that's that all right what can we see about point T well T once again is at zero so we could say T is zero zero is the opposite of 0 it is equal to negative zero then both both of them one is zero you could say zero to the left one is zero to the right well that still means that they're still on zero they're right they are zero T is equal to the opposite of the opposite of T well this would actually be true for any number for any number the opposite of the opposite is going to be that number we could have put the Q here the R here really for any number the opposite of the opposite is going to be that number again and so it's definitely going to be true for zero as well so that's definitely going to be true so hopefully that gives you a little bit more practice with number opposites and helps you digest things a little bit more