I followed your work..I think you've got it right so far!
(Except c = (-1 - y) , but you had it right in the problem.)
You are very very close to the answer. Maybe this will nudge you in the right direction.
\(x=\frac{-2\,\pm\,2\sqrt{2y\,+\,3}}{4} \\~\\ x=\frac{2(-1\,\pm\,\sqrt{2y\,+\,3})}{2(2)}\) Factor a 2 out of the numerator and factor a 2 out of the denominator.
Below is the rest of the answer if you need more help.
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\(x=\frac{2(-1\,\pm\,\sqrt{2y\,+\,3})}{2(2)}\)
Divide the numerator and denominator by 2 .
\(x=\frac{-1\,\pm\,\sqrt{2y\,+\,3}}{2}\)
Rearrange the terms in the numerator.
\(x=\frac{\pm\,\sqrt{2y\,+\,3}\,-\,1}{2} \\~\\ \begin{array}\ x=\frac{\sqrt{2y\,+\,3}\,-\,1}{2} \qquad\text{ or }\qquad &x=\frac{-\,\sqrt{2y\,+\,3}\,-\,1}{2}& \\~\\ & x=\frac{-1(\,\sqrt{2y\,+\,3}\,+\,1)}{2}&\\~\\ & x=-\,\frac{\,\sqrt{2y\,+\,3}\,+\,1}{2}& \end{array}\)
Also...for your final answer, do you need to say p-1(r) for x and r for y ?