If ⎩ ⎪ ⎨ ⎪ ⎧ x − y = 6 1 7 4 1 y − z = 1 4 1 9 7 x 1 / 7 + y 1 / 7 + z 1 / 7 = 1 2
Calculate x + y + z
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The question did not state that x , y , z were integers. How would you prove it? Or at least proof that there is only 1 solution to x + y + z ?
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I believe we can plot a graph to show it. Though may not proving it. I am attaching the plot here. It is for − 1 3 0 0 0 ≤ x ≤ 1 3 0 0 0 . Clearly there is only one solution for x .
Suppose its real , then x or y or z can be written as a fraction - such that both the numerator and the denominator are prime numbers , now 7th root will give us an irrational number , but on RHS we are having an integer , thus x,y,z varies over whole numbers
When we distribute 12 as sum of three integers, then from all the possibilities we can remove those sets of integers which have : 3 or 2 same integers. 1 as an integer. All even integers. Thus we get 3+4+5. As per conditions given in question , when crosschecked we will get x^1/7=5, y^1/7=4, z^1/7=3.
And we all used bashing....
Where do these conditions come from?
look the answer upside down
@incredible mind Not true!!!! Looking upside down, the answer comes out to be 96996
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From x 7 1 + y 7 1 + z 7 1 = 1 2 , we know that x , y and z must be integers of perfect 7 -power.
We also know that y = x − 6 1 7 4 1 , z = x − 7 5 9 3 8 and z < y < x < 1 2 7 . We can list out n 7 for n = 1 , 2 , 3 . . . 1 2 and find for n such ( n 7 − 6 1 7 4 1 ) and ( n 7 − 7 5 9 3 8 ) are also perfect 7 -powers. It is readily done with a spreadsheet and mine is as follows:
n 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 n 7 1 1 2 8 2 1 8 7 1 6 3 8 4 7 8 1 2 5 2 7 9 9 3 6 8 2 3 5 4 3 2 0 9 7 1 5 2 4 7 8 2 9 6 9 1 0 0 0 0 0 0 0 1 9 4 8 7 1 7 1 3 5 8 3 1 8 0 8 n 7 − 6 1 7 4 1 1 6 3 8 4 2 1 8 1 9 5 7 6 1 8 0 2 2 0 3 5 4 1 1 4 7 2 1 2 2 8 9 9 3 8 2 5 9 1 9 4 2 5 4 3 0 3 5 7 7 0 0 6 7 n 7 − 7 5 9 3 8 2 1 8 7 2 0 3 9 9 8 7 4 7 6 0 5 2 0 2 1 2 1 4 4 7 0 7 0 3 1 9 9 2 4 0 6 2 1 9 4 1 1 2 3 3 3 5 7 5 5 8 7 0
It can be seen that x = 5 7 , y = 4 7 and z = 3 7 . Therefore,
x + y + x = 5 7 + 4 7 + 3 7 = 7 8 1 2 5 + 1 6 3 8 4 + 2 1 8 7 = 9 6 6 9 6