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423 can be expressed as a+bc, where a, b, and c are intergers and c is squarefree. Find a+b+c.

Any help is appreciated!

 Oct 2, 2022
 #1
avatar+1633 
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a+bc=423

We can easily speculate the c = 3 (what else could c be equal to, 17!?).

a+b3=423

We can safely square both sides of the equation...

(a+b3)2=423

Open up parenthesis: a2+2ab3+3b2=423

Then we can see that the root 3 part corresponds to the root 3 part in the equation since a and b are integers:

2ab3=23

ab=1

From earlier, we also obtained:

a2+3b2=4

 

How can you take it from here to find a and b? Good luck...

 Oct 3, 2022
 #2
avatar+1633 
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you can also guess and check

proyaop  Oct 6, 2022

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