Posted by Soroban on September 25, 2002 at 19:19:25:
In Reply to: proof posted by Marin on September 25, 2002 at 14:18:55:
: How can I prove there is no integer solution to x^4 + 3x^3 = 1120 ?
: Thank you.
Look at: x^3(x + 3) = 1120
x must be a factor of 1120.
While 1120 has many factors: 1,2,4,5,8,10,16,20,...
we need to try only the first few and we're done.
x = 1: 1^3(1 + 3) = 4.... nope!
x = 2: 2^3(2 + 3) = 40... You get the idea.