Recall that in order to add and subtract fractions, they must have the same denominator. Therefore, we multiply the first fraction by (x+3)/(x+3) and the second fraction by (x-3)/(x-3) to create a common denominator of (x-3)(x+3) (which is equivalent to x2-9). The next step is to expand out and simplify the numerator;(x+2)(x+3) - (x-1)(x-3) = x2+2x+3x+6 -(x2-x-3x+3) = x2+5x+6 -(x2-4x+3) = x2+5x+6-x2+4x-3=9x+3. This leaves us with the fraction as (9x+3)/(x2-9). Our final step is to identify a and b. We can see that a=9 and b=3.