Find the number of pairs(m,n) of integers which satisfy the equation

Find the number of integer pairs ( m , n ) (m,n) satisfying the equation

m 3 + 6 m 2 + 5 m = 27 n 3 + 9 n 2 + 9 n + 1 m^3+6m^2+5m=27n^3+9n^2+9n+1

0 9 1 3

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Similar to @Brian Moehring solution, we may take both sides, mod 3

m 3 m 1 ( m o d 3 ) m^3-m \equiv 1 (mod \ 3)

Also G C D ( m , 3 ) = 1 GCD(m,3)=1 , for if m m is a multiple of 3 3 , then the RHS of the main equation should be divisible by 3 3 , which is not possible.

Since G C D ( m , 3 ) = 1 GCD(m,3)=1 , using Fermat little theorem,

m 3 m 1 ( m o d 3 ) m m 0 1 ( m o d 3 ) m^3-m \equiv 1 (mod \ 3) \implies m-m\equiv 0 \equiv 1 (mod \ 3)

which is a contradiction to the existence of any solution to the equation.

Brian Moehring
Oct 28, 2018

The given equation is equivalent to 3 ( 2 ( m + 1 3 ) + 2 m 2 + 2 m 9 n 3 3 n 2 3 n ) = 1 3\left(2\binom{m+1}{3} + 2m^2 + 2m - 9n^3 - 3n^2 - 3n\right) = 1

However, if m , n m,n are integers, then the left side is an integral multiple of 3 3 while the right side isn't. Therefore there are 0 \boxed{0} integral solutions ( m , n ) (m,n)

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...