Why is it not OK to feed a guide dog ?
Can there be a function -LSB- math -RSB- f : \ left -LSB- a , b \ right -RSB- \ rightarrow \ mathbb -LCB- R -RCB- -LSB- / math -RSB- such that -LSB- math -RSB- f -LSB- / math -RSB- is continuous at -LSB- math -RSB- x = a -LSB- / math -RSB- ?