by tommywallach Thu Feb 11, 2016 3:25 pm
They're rewriting the 1 in the denominator (the "+1" part) as x/x. This gives it a common denominator with the 1/x part, and then we can just add the numerators.
-t
P.S. I always encourage my students not to say things like "the x goes up top." This kind of thinking confuses arithmetic. Always think in terms of multiplication, division, addition, and subtraction. I don't even like the term "cancel," which muddies the clarity of the operation.