What was done from the first to the second equation was that the fraction was simplified. 126 and 32 have a common factors of 2. 126/32=(63*2)/(16*2) The 2s in the top and bottom can cancel out, leaving the fraction 63/16. In addition, since there are x terms on the top and bottom, they cancelled out as well. x/x^3=1/x^2 This leaves an x^2 term on the bottom. Thus, if a is 16, and b is 2, you will have an equivalent form of the fraction.