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Square Sides (Posted on 2024-01-01) Difficulty: 3 of 5
Find the smallest right triangle with integer sides such that the hypotenuse is a square and the sum of the legs is also a square.

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Solution Solution | Comment 5 of 7 |
So I started by parameterizing the right triangle into sides u^2-v^2, 2uv, u^2+v^2.
Then u^2-v^2+2uv and u^2+v^2 are perfect squares.

But the latter is another Pythagorean triple.  So I'll parameterize it as u=m^2-n^2 and v=2mn.
Note that in this system we need u>v, which means m^2-n^2>2mn.  This simplifies to m>n*(1+sqrt(2))

At this point I made a quick brute force program.  The first result was m=1469 and n=84
Then u=2150905 and v=246792
Then the legs of the triangle are u^2-v^2=4565486022761 and 2uv=1061652293520.  The sum is 5627138321281 = 2372159^2
The hypotenuse of the triangle is u^2+v^2=4687298610289 = 2165017^2


  Posted by Brian Smith on 2024-01-02 10:11:52
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