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Solve in Positive Integers (Posted on 2024-08-10) Difficulty: 1 of 5
Solve in positive integers:
1/x+1/y+1/z= 7/15

No Solution Yet Submitted by K Sengupta    
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Solution Solution | Comment 1 of 4
It is very easy to find a solution.   7 = 3+3+1; so 3/15, 3/15, 1/15 becomes 1/5 + 1/5 + 1/15.  So [5, 5, 15] is a solution.

But I resorted to a program to find (hopefully) all the solutions.  

{x,y,z} can be in any order, but for brevity, will show only x <= y <= z.

LCM [x, y, z]
15 [3, 15, 15]
15 [5, 5, 15]
30 [3, 10, 30]
30 [5, 6, 10]
45 [3, 9, 45]
60 [4, 5, 60]
60 [3, 12, 20]
60 [4, 6, 20]
120 [3, 8, 120]

----------
maxmultiplier = 10000
solutions = []

for mul in range(1, maxmultiplier):
    mylcm = 15*mul
    mysum = 7*mul
    myfacs = factors(mylcm)
    for comb in combinations_with_replacement(myfacs,2):
        a = comb[0]
        b = comb[1]
        c = mysum - a - b
        if c not in myfacs:
            continue
        x = round(mylcm/a)
        y = round(mylcm/b)
        z = round(mylcm/c)
        ans = sorted([x,y,z])
        if ans not in solutions:
            solutions.append(ans)
            print(mylcm, ans)

  Posted by Larry on 2024-08-10 14:56:45
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