What is the first line last line check in algebra?

The first line last line check in algebra is a method used to verify the correctness of a mathematical expression or equation by ensuring that the first line (the initial expression) and the last line (the final result) are equivalent. This involves checking that each step in the manipulation of the expression maintains equality. If the first line and last line match in terms of value, it indicates that the operations performed were valid. This technique helps catch errors in calculations or transformations.