(The latter equation in the last step is equivalent to the original equation.)
For more about canceling a zero factor, see Activity 1.
• Introducing false solutions by faulty algebraic manipulation is a very common
error. This activity illuminates this error and provides you with an opportunity
to focus students’ attention on the logic underlying the solution of equations.
In particular, the activity demonstrates the risk of applying a nonreversible
step when solving an equation.