Question

Which graph represents the function of f(x) = 9x 2 -36/3x+6 Please help

Answer 1

The function is:

             (9x^2 - 36)
f(x) = ---------------------
                3x + 6

You can simplify that function to a linear function for all x for which 3x + 6 ≠ 0

=> x ≠ - 2.

So, for x ≠ - 2, you can do:


             (9x^2 - 36)
f(x) = --------------------- =
               3x + 6

              9(x^2 - 4)
f(x) = ---------------------
                3(x + 2)

             3(x + 2)(x - 2)
f(x) = --------------------- = 3(x - 2) = 3x - 6
                 (x + 2)

So, the graph is a right line that intercepts the y-axis at - 6 and the x-axis at x = 2, excluding x = -2 as the function is not defined for x = -2. That is the second graph of the second picture.