Question 1d4f9e0d

Advanced Math - Nonlinear equations in one variable and systems of equations in two variables

In the xy-plane, a line with equation $2 y equals c$ for some constant $c$ intersects a parabola at exactly one point. If the parabola has equation $y = - 2 x^{2} + 9 x$ , what is the value of $c$ ?