Bestem ccc slik at f(x,y)=c(x+y)f(x,y)=c(x+y)f(x,y)=c(x+y), x,y∈{0,1,2}x,y\in\{0,1,2\}x,y∈{0,1,2}, er en gyldig simultanfordeling.
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Krav: ∑x∑yc(x+y)=1\sum_x\sum_y c(x+y)=1∑x∑yc(x+y)=1. ∑x=02∑y=02(x+y)\sum_{x=0}^{2}\sum_{y=0}^{2}(x+y)∑x=02∑y=02(x+y): hver xxx bidrar ∑y(x+y)=3x+(0+1+2)=3x+3\sum_y(x+y)=3x+(0+1+2)=3x+3∑y(x+y)=3x+(0+1+2)=3x+3, summert over x=0,1,2x=0,1,2x=0,1,2 gir 3+6+9=183+6+9=183+6+9=18. Altså 18c=1⇒c=11818c=1\Rightarrow c=\tfrac{1}{18}18c=1⇒c=181.
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