  Using elementary number theory we study Diophantine equations over the
rational integers of the following form, $y^2=(x+a)(x+a+k)(x+b)(x+b+k)$,
$y^2=c^2x^4+ax^2+b$ and $y^2=(x^2-1)(x^2-\alpha^2)(x^2-(\alpha+1)^2).$ We
express their integer solutions by means of the divisors of the discriminant of
$f(x),$ where $y^2=f(x)$.
