The Goal

Simplify the expression:

The Mistake

Find the algebra mistake:

Need a hint? Look carefully at the red part of the algebra:

The Correction

An Explanation

If we look carefully at the mistake, we see that the expression has the form

which the student has mistakenly rewritten in the form

But only common factors of the numerator may be rewritten this way, for example, if the expression had the form

then it could be rewritten as follows:

A nice way to simplify the original expression is to multiply by 1 in the form shown in "The Correction", chosen so that the negative exponent factors in the numerator are cleared.