Distribute 2pr into the parentheses (r+h)
to remove the parentheses:
Get the term that does not contain h off the right side, by
subtracting 2pr2 from both sides:
Divide both sides by what is multiplied by h on the right side,
which is 2pr
We have to be careful here. Although it is perfectly correct
to cancel 2pr on the right side, since EVERYTHING IS MULTIPLIED.
However, we MUST NOT CANCEL anything on the left side because
the numerator is a SUBTRACTION, not a MULTIPLICATION. So
cancel on the right, but leave the left side as it is.
Edwin
