For the question:
Show that the equation (x^2 + 5x)/(7x + 9) = (1 - k)/(1 + k) has real roots for all values of k.
I know that for real roots, the discriminant has to be greater or equal than 0. I found out the discriminant, which is x^2 + kx^2 - 2x + 12 xk - 9k + 9 greater than or equal to 0. How do I make it into a quadratic equation?