Rio de Janeiro is one of the states of Brazil, on the southeastern coast. Its capital is the city of Rio de Janeiro, which was the colony's capital from 1764 (the first being Salvador da Bahia), and the nation's capital from 1822 to 1960.
... a constant (i.e., in this case, a quantity that does not depend on x) to the expression to the left of "=", that will make it a perfect square trinomial of the form x2 + ...