What are the discontinuity and zero of the function -LSB- math -RSB- f -LRB- x -RRB- -LSB- / math -RSB- of -LSB- math -RSB- \ frac -LCB- 9x ^ 2-36 -RCB- -LCB- 3x +6 -RCB- ? -LSB- / math -RSB-
Is the function -LSB- math -RSB- f -LRB- x -RRB- = \ frac -LCB- x ^ 2 -- 16 -RCB- -LCB- x +4 -RCB- -LSB- / math -RSB- discontinuous at -LSB- math -RSB- x = -4 -LSB- / math -RSB- ?