See: List of heritage railways, Heritage railways in the Republic of Ireland, railway, mountain railway, List of Conservation topics, Conservation in the United Kingdom
... so we add the square of b/(2a) to both sides, getting <math>x^2+\frac{b}{a}x+\frac{b^2}{4a^2}=-\frac{c}{a}+\frac{b^2}{4a^2}.</math> The left side is now a ...