How many integral solutions are there to x+y+z+w=29 ,where x≥1, y≥2, z≥3x and…
2023
How many integral solutions are there to x+y+z+w=29 ,where x≥1, y≥2, z≥3x and w≥0?
- A.
2400
- B.
2600
- C.
2800
- D.
3000
Attempted by 7 students.
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Correct answer: B
First, address the likely typo in the constraint z ≥ 3x by assuming it means z ≥ 3 to match standard problem types.
Transform variables to remove lower bounds: let x' = x-1, y' = y-2, z' = z-3, and w' = w. The equation becomes x'+y'+z'+w' = 23.
Apply the stars and bars formula C(n+k-1, k-1) with n=23 and k=4 variables. This results in C(26, 3).
Calculate the combination: (26 × 25 × 24) / 6 = 2600 integral solutions.
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