Brain teaser

35

Posted by: @mathteacher

Is there a way to solve this other than trying each value? Properties of integers is not one of my strong suits.

Posted by: @mathteacher

35

You forgot the squaring of y.

Posted by: @dave-lindell

My spreadsheet says 2954 is close.?ÿ Nope.?ÿ It isn't an integer solution.

That is a very difficult problem and forms the basis of some Internet encryption.?ÿ The solution could be in the tens of billons if y > (a big number).?ÿ I poked around and could find no easy way to solve it.?ÿ I suspect your problem is a teaser and is unsolvable without big iron supercomputers.

If someone pops up with the solution I'll be mightily impressed.

@bill93

The square root of the sum of 1 and 1729 x 2954 x 2954 is 122831 exactly

There may be a smaller answer, though.

Posted by: @holy-cow

Nope.?ÿ It works to the precision of my calculator, but the expression yields 15087454565 and 122831^2 is 15087454561.

You can see that it doesn't work just by keeping only last digits in your head as you work through it, and not worrying about the rest of the big product digits.

@bill93

I agree.?ÿ I goofed.

After additional research I found that

is prime so the problem reduces to y2 = 2^ 668122 to solve for y which is no trivial task.?ÿ I'm convinced it's an even number though because of the +1 factor.

?ÿ

@holy-cow Nope, I get 122831.00001628253453824718136713 which is well within the accuracy of my crappy 64 bit calculator so y is not = 2954.

Plenty good enough for setting a monument though and I'd be miffed if you pincushioned?ÿ my mon 0.00001' next to it.

Posted by: @mike-marks

You totally lost me on how you got there from the initial problem posted.

The answer is obviously Pi. Pi is the answer to almost all things. If not, it's Avogadro's number: 6.02 x 10 to the 23rd.

If I ever need to solve the problem the OP presented as a matter of land surveying, I shall turn in my license. I am confident my license is not at risk.

Ignore The Hitchhiker.................it ain't 42.............

I get the same number as the MathTeacher?ÿ "35"

JOHN NOLTON

If y=0 isnt ok then

y=1729*13!?ÿ which is the integer 10766518963200

The side of the square is then?ÿ 447685271124001

?ÿ

not so small?ÿ ?????ÿ

Not quite. That number is actually 447685271124000.969078681, truncated at 9 decimal places.

This site may have enough capacity to find the answer, or it may not:?ÿ https://www.mathsisfun.com/calculator-precision.html

?ÿ

@bill93

Not mine, either. I'd be a bad choice for a crypto job.

Posted by: @john-nolton

Only if you leave off the squaring of y.

@mike-marks

The square root of 2^668122 is just 2^334061; take half the exponent. But, we want 1729*y^2+1 to be a perfect square and your y produces a prime number for that expression, which can't be a perfect square.