if , then we can write the equation in the form of you're done. but if you want the form , just factor the numerator by completing the square.
If E = 0, then you have the quadratic equation
note that if you use the quadratic formula in solving x, is the determinant, and if it is zero, you will be left with constant
same with b). but here, note that for a quadratic equation in one variable, if the discriminant is positive, then you have two solutions for the variable, hence, you have two vertical lines.