If f(x) = (x + 4)/(x^2 + ax + b) and f(x) has two vertical asymptotes at x=1 and x=2, then find the sum of a and b.
For rational functions, asymptotes occur when the denominator is 0.
Then x = 1 and x = 2 are roots of x^2 + ax + b = 0.
Using some precalculus, a = -3 and b = 2.
The value of a + b is obvious at this point.