A-REI.A. Understand solving equations as a process of reasoning and explain the reasoning.
A-REI.A.1. Explain each step in solving a simple equation as following from the equality of numbers asserted at the previous step, starting from the assumption that the original equation has a solution. Construct a viable argument to justify a solution method.
A-REI.A.2. Solve simple rational and radical equations in one variable, and give examples showing how extraneous solutions may arise.