Question 32202
x² + x - c = 0
using the quadratic formula,
{{{x = (-1 +- sqrt( 1+4c ))/2 }}}
Let D = 1 + 4c
For integer solutions for x, we require {{{sqrt(D)}}} must be odd.
.: D = odd*odd = odd
.: 1 + 4c = odd
4c = even
=> c = even
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