As perfect as a square! 2

Positive integers a , b , c a, b, c are distinct from each other. Given that

  • None of them alone is a perfect square
  • All the products a b , b c , a c ab, bc, ac are perfect squares

Find the least value that a + b + c a + b + c can take.


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24 28 I like cookies 10 45

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3 solutions

Ethan Mandelez
Mar 27, 2021

A perfect square is the product of some integer with itself.

In this case, let a = a 1 a 2 a = a_{1}a_{2} , where a 2 a_{2} is the largest square dividing a a . Likewise, let b = b 1 b 2 b = b_{1}b_{2} and c = c 1 c 2 c = c_{1}c_{2} . Since a b , b c , a c ab, bc, ac is a perfect square, a 1 = b 1 = c 1 = x a_{1} = b_{1} = c_{1} = x for some value x x in which a , b , c a, b, c are not perfect squares. Therefore the smallest possible value of x x must be 2 2 , and the smallest possible values for a 2 , b 2 , c 2 a_{2}, b_{2}, c_{2} are 1 , 4 , 9 1, 4, 9 in some order.

Therefore we can conclude that

a + b + c = 2 × 1 + 2 × 4 + 2 × 9 = 28 a + b + c = 2 \times 1 + 2 \times 4 + 2 \times 9 = 28

Then what are the values of each a , b , and c a, b, \text { and } c ?

. . - 2 months, 2 weeks ago

2, 8, 18 in some order 👍

Ethan Mandelez - 2 months, 2 weeks ago

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Yeah!! I guessed it and got this.

Wahyu Adi - 3 weeks, 4 days ago

I guessed it after a few cases, nice proof!

Vinayak Srivastava - 2 months, 1 week ago

Thank you!

Ethan Mandelez - 2 months, 1 week ago

Isn't 1 a perfect square ?

j h - 1 day, 12 hours ago
Veselin Dimov
Mar 28, 2021

...but I like cookies

haha me too :D

Ethan Mandelez - 2 months, 2 weeks ago

Which cookies- this cookie or this cookie ?

Vinayak Srivastava - 2 months, 1 week ago

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I know it is a bad joke...

Vinayak Srivastava - 2 months, 1 week ago

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I love only chocolate cookies. @Vinayak Srivastava .

. . - 2 months, 1 week ago

haha it is, but nice try 👍

Ethan Mandelez - 2 months, 1 week ago

Not interested

Sourav Saha - 2 months ago

SAME HERE 🍪

CARLE JOES - 1 month, 3 weeks ago

Mine's too.

Wahyu Adi - 3 weeks, 4 days ago
André Hucek
May 23, 2021

The answer should've been "I like cookies". Everyone likes cookies...

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