p(x，y)= 1/4 (x，y)∈G

0 others

P (at least one of x and y is less than 1)

= 1-P(X≥ 1，Y≥ 1)

= 1-∫∫[x & gt； 1，y & gt 1] p(x，y)dxdy

= 1-∫∫[ 1≤x & lt； 2 1≤y & lt； 2] 1/4dxdy

= 1- 1/4

=3/4

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