Question 1089718
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I agree with the solution by @josmiceli,  and only want to add that 


together with the triple ((a,b,c) = (8,-2,-15)  any other triple which is multiple to this one, is also the solution.


For example, triples (a,b,c) = (16,-4,-30)  and (-8,2,15)  also are the solutions.
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