Number of reduced binary quadratic form of determinant $d$ Is finite
In the proof, book consider positive and indefinite quadratic reduced form giving them upper bound and saying that it proves reduced quadratic forms are finite. But why we don't consider negative definite quadratic forms ? ( An Introduction to The theory of numbers - Ivan Niven , Theorem 3.19 )
I searched in the internet but didn't find anything that clarify it. I didn't add add the proof, because it only talks about upper bound of the positive and indefinite binary quadratic forms.