2x + 3 6. (6 points) Let f(x) = (a) (4 points) Find the derivative of f at a = 3 using the definition of the derivative as a limit. Make sure to explain your computations, including justifying why you are able to evaluate any limits. You will get no credit for using any differentiation rules like the quotient rule or power rule. (b) (2 points) Find the equation of the tangent line to the graph of f at x = 3. Briefly explain your