Checking an absolute value equation for extraneous solutions

Solve the equation. Check for extraneous solutions.
|4x| = 28

Absolute value is the distance away from zero. 

|4x| = 28
4x = 28 or 4x = -28   {the two numbers that are 28 away from zero are 28 and -28}
x = 7 or x = -7   {divided each side by 4} 

Check. If it makes a false statement, then it is an extraneous solution. 

Check 7:
|4(7)| = 28
|28| = 28   {multiplied}
28 = 28   {true statement, so 7 is not extraneous} 

Check -7:
|4(-7)| = 28
|-28| = 28   {multiplied}
28 = 28  {a true statement, so -7 is not extraneous}

- Algebra House