Solve (pen and paper only):
List all possible integer solutions.
a few very small steps:
clearly x is not negative else the LHS is not integer.
x = 0 and y= +/- 3 is a solution.
for all y that work, so does -y, as LHS is positive
x are even, since this produces LHS numbers ending in ..09 and ...49
(x odd makes numbers ending in 19 and 39 which can not be squares)
likewise y ends in 3 or 7
I wonder how 5*3^x=(y-2)(y+2) might help
Edited on October 10, 2018, 5:24 pm