Find the number of integer solutions x1+x2+x3=20 with x1≥0 x2≥1 x3≥1 is this C(20,2)? Thank you.
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How did you get that result?
Take y2 = x2 - 1 and y3 = x3 - 1
Rephrase to x1 + (y2 + 1) + (y3 + 1) = 20 or x1 + y2 + y3 = 18
And out pops C(18+2,2). I think you have it!
Originally Posted by tinabaker Find the number of integer solutions x1+x2+x3=20 with x1≥0 x2≥1 x3≥1
is this C(20,2)? When posting please do not use special fonts.
The number of way to put N 1's into K variables is .
If we want we can think of putting a 1 into each of those two variables.
So is the answer
thank you for your help
If you require all x's to be 0 or greater, the equation is ((N-1)C(K-1)).
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