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This problem, we have been given three sets and we have been asked to list the elements of the set y cross x, cross y, cross z.
00:08
Now, this will be the set of all ordered four pupils, says that the first component is an element of y, the second component is an element of x, the third component is an element of y, and the fourth component is an element of z.
00:22
So let us draw a tree diagram.
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First of all, the first component is an element of y.
00:27
Now there's only one element in y, that's a.
00:30
The second component will be an element of x.
00:33
X has two components, sorry, x has two elements, one and two.
00:38
And the next component is an element of y.
00:41
Y has only one element which is a...